MINNEAPOLIS (AP) -- State investigators have started working to find out why an underground natural gas pipeline ruptured in Minneapolis, causing a huge explosion and a tower of fire.

The blast Thursday sent flames spewing skyward just 100 yards from a busy freeway and near the entrance of a grocery store. Fire officials say amazingly no one was injured.

CenterPoint spokeswoman Rebecca Virden says the gas company wasn't doing any work on or near the pipe before it ruptured.

Virden says the 20-inch pipe is inspected twice a year at minimum. The blast and fire scorched parked vehicles and opened a large hole in the street near the entrance to Cub Foods. Homes and businesses in an eight-block area surrounding the fire were evacuated for several hours.

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