Firefighters Tuesday morning were monitoring a fire in Erie, Ill., after a gas line exploded during the night, the company that owns the line said, according to UPI. The cause of the explosion, which took place 11:30 p.m. CDT Monday, was not immediately determined, and fire crews were waiting until daylight to investigate and repair the line, WHBF-TV, Moline, reported. A spokesperson for Enterprise Productions said there are thousands of miles of gas lines -- of propane and ethanol mix -- in the area. Thirty-seven people living within a mile of the explosion were evacuated. All but the people living in two homes were allowed back to their residences as of 4 a.m, WHBF said. Witnesses told the broadcaster flames from the explosion could be seen from miles away.