Four workers from the Louisiana Department of Transportation and Development were hospitalized after a drum of illegally dumped muriatic acid ruptured in Algiers on Wednesday morning, according to the New Orleans Fire Department.

The crews were removing the chemical-filled plastic drums from beneath an overpass in the 6000 block of Woodland Highway.

About 8 a.m., one of the 30-gallon drums began leaking. Muriatic acid, which is derived from hydrochloric acid, is corrosive and can irritate the eyes, nose and respiratory tract, according to the U.S. Environmental Protection Agency.

The four workers were overcome by the vapors and taken to West Jefferson Medical Center in Marrero, the fire department said. They were later released.

About 33% of the drum’s contents leaked, according to authorities. The Fire Department’s hazardous materials unit was dispatched and set up a 100-foor perimeter around the scene. Cleanup was still underway as of 1:30 p.m.