CHICAGO (CBS) – Explosions rocked parts of Willowbrook and Westmont Friday after gasoline leaked into the sewage system.

Westmont officials say it will take several days to fully clear gas from the groundwater. All signs point to a leak from a nearby gas station as the source.

Some in the area are still without electricity. People who live down the road from the gas station were allowed to return home overnight. One woman remains hospitalized with burns.

Her neighbors at the Knolls condominium complex in Willowbrook say the victim was doing laundry when something exploded Friday morning.

By the end of the day, firefighters responded to about nine other flashes and fires. They also checked out hundreds of reports of gas odors.

Investigators eventually determined the source: a Speedway gas station in Westmont. They believe fuel leaked from the station into the sewer system that stretches about eight miles.

Westmont Deputy Fire Chief James Connolly explained what crews would be doing today.

“Ventilating the system, tracking product, putting emulsifier in the system to reduce any vapors,” said Connolly. “Speedway and their contractors removed approximately 60,000 gallons of water and gasoline mixture. That doesn’t mean it’s all gasoline. It’s a mixture of water and gasoline. We believe we have the source of the problem isolated.”

Experts from the Environmental Protection Agency and the state fire marshal will conduct separate investigations into the gas leak.

Westmont’s Deputy Fire Chief said the gas tanks in the area are roughly 20 years old.

The Speedway remains closed until further notice.

A Facebook update from the Willowbrook Police Department says the sewer is cleared of fuel but workers will continue to monitor it.

The Red Cross has set up a reception center at Hinsdale South High School for those impacted by the Willowbrook explosion.