A bright greenish-yellow liquid gushed onto the side of a Michigan highway Friday, prompting a multiagency investigation that discovered the mystery substance was probably a chemical that is known to cause cancer.

The hexavalent chromium-contaminated water that rushed from a retaining wall onto Interstate 696 in the Detroit suburb of Madison Heights appeared to come from a shuttered electroplating business, said Jill Greenberg, a spokesperson for the Michigan Department of Environment, Great Lakes and Energy.

The department forced the business, Electro-Plating Services, to close in 2016 after inspectors found hundreds of containers of hazardous waste at the site. The owner, Gary Sayers, is serving a year in federal prison after pleading guilty to illegally storing the waste.

Hexavalent chromium is usually created by an industrial process like plating or welding, according to the Occupational Safety and Health Administration. It is toxic and particularly harmful to the respiratory system, kidneys, liver, skin and eyes.

The Environmental Protection Agency took samples of the contaminated water Friday to confirm that the substance is hexavalent chromium, Greenberg said. Results are expected this week.

There is no imminent risk to the public and no impact on air or drinking water, Greenberg said. She said hexavalent chromium is most dangerous if someone inhales it or touches it. The highway’s shoulder was closed during cleanup to prevent people from approaching.

Investigators say they believe the liquid traveled in an underground drain from the building’s basement, down an embankment toward the freeway and through a crack in a concrete retaining wall on the eastbound side of the highway, Greenberg said. The liquid froze into a blob once it reached the street, according to Michigan State Police.

Officials have cleaned the contaminated water from sewers and storm drains, Greenberg said. They are using a sump pump in the basement of Electro-Plating Services to move the liquid into a portable tank and keep it from migrating off-site.

Authorities will then decide what kind of long-term remediation is necessary, Greenberg said. The EPA removed the hazardous chemicals from the business when it was closed, but did not fix soil or groundwater contamination, the Detroit Free Press reported.

Environmental activist Erin Brockovich made hexavalent chromium famous in the 1990s by fighting against its presence in California drinking water. Her work inspired a 2000 movie named after her.

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