EDWARDSVILLE, Ill. – Two construction workers were found dead inside a manhole at a residential development Friday in Edwardsville, Illinois.

The incident happened at the 100 block of East Union Street. Edwardsville police responded to the scene around 6:55 p.m. and found two men inside a manhole. Police said the men had been working in an underground area that led to storm sewer piping.

An officer tried to help but the victims were pronounced dead on the scene. That officer had to be transported to a nearby hospital with non-life threatening injuries.

Fire Chief James Whiteford said there was a buildup of toxic gases in the area where the construction workers were found, which is common in confined underground spaces.

The workers’ bodies were recovered around 8:30 p.m.

The deceased men’s names have not been released. The investigation is still ongoing.