At about 5:45 p.m. Sunday evening, firefighters began evacuating homes after mounting complaints of a foul smell emanating from area basements. Although authorities remain unsure specifically what gas caused the noxious fumes, they were able to trace the leaks to sump pumps in multiple residents' homes.
"Honestly, at this point, it would be pure speculation and I don't want to get into it," Skippack Township Fire Chief Haydn Marriott told Philadelphia's 6 ABC news.
"All we know at this point is that the substance that was in the sump pump pit tested positive for some sort of hydrocarbon."
Samples of the odor causing gas have been collected by the Environmental Protection Agency and results are expected to be announced Monday afternoon
Notable deaths of 2014 [PHOTOS]