A natural gas explosion late Wednesday overturned cars and blasted a hole in a parking lot at a shopping mall on the city's southwest side, authorities said. Ten people were hurt.

The cause of the explosion at the Ford City Mall (search) was unknown, authorities said. Utility crews were on the scene to shut down gas service to the area. Ambulances and other emergency crews also responded.

Three of the injured were taken to the hospital in serious condition, while the others were in fair or good condition, Chicago Fire Department (search) spokeswoman Rosa Escareno said.

A piece of a gas main landed inside a restaurant at the mall, she said. "We have a lot of broken glass, damaged vehicles and a pretty good-sized hole in a parking lot," added Larry Langford, another fire department spokesman.

The blast overturned several cars, including at least one with people inside, Escareno said. The people in the car apparently escaped injury.