Officials are saying power has been restored to much of the Knolls of Willowbrook condominium complex and many residents have been allowed to return home following Friday morning's blast.

The fuel contamination in the sewer line that is believed to have caused the explosion is also believed to have been removed.

Investigators believe fuel leaked from a Speedway gas station at 6241 S. Cass Ave. just north of 63rd Street in Westmont into the Flagg Creek Water Reclamation District sanitary sewer system and local storm sewers.

More than 100 reports of noxious odors in the area and at least 10 flashes and/or explosions and fires occurred -- mostly along 63rd Street between Cass Avenue and Route 83.

The initial explosion, at about 9:30 a.m. Friday, left one building in the Knolls of Willowbrook condominium complex on the 6200 block of Knollwood Drive uninhabitable, authorities said. It was sparked by an elderly woman using a laundry facility in a common area of the building.

"The situation in the Knolls complex is currently secure. The affected building on Knollwood Road has been secured with police officers on scene overnight," Willowbrook Police Chief Robert Pavelchik said Saturday morning. "The Tri-State Fire Protection District personnel and their mutual aid partners were able to examine all of the other buildings and then allowed the residents to return. At this time, ComEd has restored power to most of the other buildings in the complex."

Crews also worked through the night to ventilate the sewer system that runs for about 8 miles along 63rd Street to the water reclamation district plant near I-294 and I-55. They also added emulsifier to reduce the harmful vapors.

Friday night officials said Speedway and their contractors have removed approximately 60,000 gallons of the water and gasoline mixture from the sewer system.

"I believe that the sewer system has been cleared of the contamination and is still being monitored for hazards," Pavelchik said.

Tri-State Fire officials did not immediately return emails seeking updates.