Published: Mar 17, 2011 4:31 PM EDT
Updated: Mar 17, 2011 1:33 PM EDT

MINNEAPOLIS- A natural gas line exploded in south Minneapolis on Thursday, sending flames shooting high into the sky, scorching nearby vehicles and forcing authorities to temporarily evacuate nearby residents.

Assistant Fire Chief Cherie Penn told reporters the gas has been shut off, and that there are no known injuries.

The initial blast around 8:30 a.m. left a large hole in the road in front of a Cub Foods supermarket near the interchange of Interstate 35W and Highway 62. Cars in the parking lot were scorched in the blast.

Penn said a second explosion rocked the area a little later. The flames died after authorities shut off the gas line at about 10:30 a.m.

Gas levels in the air had reached 80 parts per million but are back down to zero, Penn said.

"I think the situation is as under control as it can be," Mayor R.T. Rybak told reporters.

A major trunk gas line for that section of Minneapolis exploded, and state pipeline safety officials are on the scene, according to Rebecca Virden, a spokeswoman for CenterPoint Energy. She said it was too early to determine the cause.

Witness Len Slade said that before the explosion and saw a black liquid spewing from the ground near the supermarket.

"It looked like when you see an oil well bubble up out of the ground, like when they strike oil," he said.

Slade, a vice president with Jerry's Enterprises, which operates the store, said he was in the doorway of the store, across the sprawling parking lot from the blast site, when something ignited with a poof. He said the heat was so intense that he had to retreat into the building.

"You could feel the heat coming through the front door," he said.

Kiara Jones said a neighbor called to tell her she had to evacuate her home about three blocks from the blast."You could feel the heat outside my house," Jones said. "They said the manholes might blow."

An apartment complex, day care and church near the scene were evacuated, and people inside the grocery store were told to leave through the back. One school was evacuated and were put on lockdown. School officials planned to keep students indoors for the rest of the day.

By late morning people were being allowed to return to everywhere but the immediate area around the supermarket.

On Sept. 9, a natural gas explosion in San Bruno, Calif., sparked a massive fireball that killed eight people and destroyed three dozen homes in the suburb overlooking the San Francisco Bay.

The investigation and recriminations continue. Earlier this week, California regulators said they planned to fine Pacific Gas & Electric Co. up to $1 million a day for failing to turn over key safety records.

PG&E spokesman Joe Molica has said the company is not yet satisfied with the results of its records search.

Just over a year ago, another natural gas explosion destroyed a St. Paul home, prompting a lawsuit and forcing Xcel Energy Co. - the Twin Cities' other major gas provider - to start a sweeping process to make sure it didn't happen again.

State regulators quickly ordered Xcel to create a plan to fix other gas lines that had been inadvertently pierced by sewer pipes or face a $1 million fine. The effort was expected to take three years. As of last month, the Star Tribune reported that 25,000 sewer lines had been inspected at a cost of about $4 million. Fifty-seven of the so-called "cross bores" were located and repaired at no cost to customers.

(Copyright 2011 by The Associated Press. All Rights Reserved.)