Officials say a total of three people were transported to a local hospital with shortness of breath. Their ages were not immediately released. They were reported to be in stable condition.
The manhole was uncovered by utility workers. Los Angeles County Fire Department officials say they received a call from the Public Works building at Euclid Street and Electric Avenue saying the employees were being overcome by a foul odor coming from the sewer.
The substance emitting the odor was identified as some kind of de-greaser, according to authorities.
People inside surrounding buildings were told to stay inside and not venture outside until officials have cleared the situation. A hazmat team was on scene.