Mysterious Black Goo Has Been Tormenting Venezuela For 40 Years

The La Mancha Negra plot thickens, as does the goo.


Charlie Haigh


Charlie Haigh

Marketing Coordinator & Writer

Charlie is the Marketing Coordinator and Writer for IFLScience, she’s currently completing a undergraduate degree in Forensic Psychology.

Marketing Coordinator & Writer

Edited by Laura Simmons
Laura Simmons - Editor and Staff Writer

Laura Simmons

Editor and Staff Writer

Laura is an editor and staff writer at IFLScience. She obtained her Master's in Experimental Neuroscience from Imperial College London.

The surface of liquid bitumen mastic, background.

The goo definitely existed, but pretty much everything else is speculation.

Image credit: koodesnica71 /

In 1986 Venezuela, a peculiar, venom-esque goo began seeping from a busy highway connecting the Simón Bolívar International Airport and the capital city of Caracas. As quickly as it appeared, the mysterious goo, named La Mancha Negra or the black spot, began to spread, turning the highway into a motorist death trap.

The black goo first appeared on a 46-meter (50-yard) patch of asphalt on the highway and continued to grow until it eventually covered roughly 13 kilometers (8 miles), with a thickness of 2.5 centimeters (1 inch) in places. Appearing as a black tar-like substance, the goo was said to have the consistency of chewing gum. In the first five years of its existence, La Mancha Negra reportedly took the lives of 1,800 people who attempted to traverse the road it engulfed.


Despite disappearing briefly and without reason in the 90s, La Mancha Negra made its comeback again in 2001, as mysterious as ever. But what was this oozing substance, and where did it come from? Even now, La Mancha Negra remains a mystery, and, like any good mystery, it comes with its own set of conspiracy theories.

Where did the goo come from?

The discourse around La Mancha Negra is sparse, tentative, and chock-full of speculation, but there are a few fan favorites when it comes to theories surrounding the cause of the ooze.

One theory is that it was caused by a bad batch of asphalt, which would explain its tar-like appearance. Asphalt contains tar which, when heated, gets sticky, and, like tar, one of the key features of La Mancha Negra is its reactivity to weather, growing when it's hot and rainy, and shrinking again when the temperature and humidity drops.

Another theory posits that the goo is a result of natural petroleum deposits nearby. The city of Caracas sits near the Orinoco Belt which uses pipelines to transport heavy oil to Caracas and other Venezuelan cities. However, Ramanan Krishnamoorti, PhD, a professor of chemical and petroleum engineering at the University of Houston, told Popular Mechanics that “usually such oozing from a reservoir’s subsurface would have to be at a single failure point and not likely to spread over an eight-mile length of the road.” Going on, he explains, “Also, typically heavy oils will settle and not try to ooze out onto the surface.”


Reinaldo Gonzalez, PhD, a lecturer at the University of Houston in the petroleum engineering department who was in Venezuela during the 1986 occurrence also explained his preferred theory in a statement to Popular Mechanics: “The simplest possible explanation that I seem to remember is that the phases of the treated asphalt separated, and one of them ‘emerged’ to the surface, causing a kind of black and slightly greasy stain on the roads.”

In yet another theory, claims were made that raw sewage from the nearby slums was to blame, speculating that it caused a chemical breakdown of the asphalt as it flowed downhill under the roads. Others think it was the result of burnt rubber from tyres or oil falling from car engines. 

But the more outlandish, and perhaps more entertaining claims, are that the goo was created on purpose by people working for, or against, the Venezuelan government.

Government involvement

During the 1980s, when the goo first appeared, Venezuela was led by Jaime Lusinchi who saw a short term in office from ’84 to ’89, during a brief intermission between Carlos Andres Perez’s two terms. During this period, the country dealt with copious scandals in the form of government corruption and embezzlement, largely involving money made from Venezuela’s enormous oil reserves.


Venezuela has one of the largest oil reserves in the world and is colloquially referred to under the derogatory name “petrostate” due to its reliance on these oil and natural gas deposits, as well as its periods of widespread corruption. So, when the price of oil began to plummet in the 1980s, and a tar-like substance began leaking from the capital’s busiest highway, people began to get suspicious.

A leading theory speculates that the faulty asphalt was a result of mismanaged government funds, whereby corners were cut, and money was saved by using sub-standard materials in road repairs and maintenance.

Similarly, there’s speculation that the government and private companies were both making heavy profits by repeatedly botching repairs to the road and elongating clean-up efforts, a theory that was flamed by the persistence of the problem and the seemingly sub-par attempts to try to remove it and find out what it was.

Some even speculated that the original blob was intentionally created to sabotage Perez and make his government look bad as he left office in 1984. However, Perez returned to office again in ’89, meaning the goo’s theorized mission was unsuccessful in tar-nishing public opinion of Perez.


Additionally, a later theory reported on by French news agency Courrier National in 2003 recounts claims made by Caracas mayor Freddy Bernal in 2001, when the goo made its second appearance. He reportedly claimed that hired people were throwing bags containing used oil onto the highway under the cover of night in an attempt to tarnish his reputation.

Despite reported claims from Bernal that alleged that samples were found to contain 60 percent brake fluid and 40 percent used oil, indicating the substance was made intentionally, the claims haven’t been substantiated and fail to account for the initial oozing occurrence.

The Venezuelan government did, however, reportedly spend millions trying to investigate the composition of the goo, but despite hiring experts from the US, Canada, and Europe, their chemical tests supposedly weren’t able to verify what was in the substance.

Where did it go?

During the goo’s reign of terror, continuous efforts were made to pressure wash it away with water and air and scrape the sticky substance off the road’s surface, but all attempts were in vain, with the ooze seeming to spread straight back again.


Attempts were even made to dry the sludge by dumping pulverized limestone on the road, but this only worked to create more issues when the dust from the limestone began affecting the air quality and visibility in the area.

Car pileups became common on the busy highway road, on which copious red warning signs were erected in an attempt to slow traffic. Local residents and taxi drivers would avoid driving on the highway, and the area was closed four nights a week while workers attempted to temporarily restore the road’s surface.

But, while the goo did increase the rate of car crashes in the area, even the total number of deaths caused by La Mancha Negra is speculated. The 1,800 figure is claimed to have occurred in just the first five years of the sludge’s existence – that’s around one death on the road per day – and no figures have been given about the subsequent deaths after that time. Many reports of the event emphasize the lack of supporting evidence to substantiate these exact figures.

Regardless of the exact details of the goo controversy, it did cause a very real disruption in the country for many years, before making an abrupt and unexplained disappearance in the 90s. It’s still not entirely clear what stopped it, but it’s speculated that large mudslides in 1999 that necessitated the building of new roadways could have played a part.


However, those pesky new roads weren’t about to stop La Mancha Negra, as it made its second (and supposedly final) appearance in 2001. Official reports on the current progress of La Mancha Negra seem to have stopped in the early 2000s, with all recent accounts citing these older pieces as the most recent sources.

For this reason, it’s widely speculated that La Mancha Negra finally reached its demise sometime in the late noughties, and it doesn’t seem to have returned. How this happened, though, is still up for debate.


  • tag
  • mysteries,

  • goo,

  • Venezuela