CUPERTINO -- (Published Sept. 2, 2011)

Federal investigators are looking into the explosion of a leaky Pacific Gas and Electric Co. gas line that devastated a Cupertino condominium, officials said Thursday.

It took PG&E crews about an hour and a half to cut the flow of gas after the explosion and fire ripped through the condo at 12:30 p.m. Wednesday, just 15 minutes after its owner had left for lunch.

No one was hurt, but the condo is a total loss.

When crews examined the 2-inch plastic distribution pipe feeding smaller lines running into and around the condo at 20299 Northwest Square, they found a total of seven leaks, PG&E said.

The explosion came just one day after PG&E was harshly criticized by the National Transportation Safety Board for its handling of gas safety in light of the San Bruno blast last year that claimed eight lives, and a 2008 explosion outside a home in Rancho Cordova (Sacramento County) that killed its 72-year-old owner.

In both disasters, regulators took issue with the length of time it took PG&E to shut off the gas.

The California Public Utilities Commission said it is investigating the Cupertino explosion.

Federal scrutiny

Kelly Nantel, a spokeswoman for the National Transportation Safety Board, said her agency would take a heightened interest in the state's probe in light of PG&E's troubled track record. The federal agency does not normally investigate an explosion that does not result in loss of life or extensive damage, she said.

"We are going to look at any commonalities this may have had with other investigations," Nantel said, "and will take any appropriate follow-up action. Given our recent experience with investigating accidents in California, we think this is an appropriate level of involvement."

PG&E officials acknowledged that it took crews until 2:30 p.m., two hours after the explosion, to shut off the gas. Fire officials said the company's workers had arrived about 30 minutes after the first report of an explosion.

Rooms in flames

Santa Clara County fire Capt. Gil Smith said he had arrived soon after the blast to see that the garage door of the condo unit was blown off and several rooms were in flames. The blaze inside was quickly put out, but the fire continued to burn at spots near where the gas was leaking in front of the unit, he said.

Smith said PG&E crews had to dig with a backhoe in three places on the line before finally managing to pinch off the gas flow. The Fire Department's chief, Ken Kehmna, said PG&E did not have a nearby central shutoff valve that could stop the flow quickly.

PG&E came under sharp criticism from the National Transportation Safety Board for having only manual shutoff valves instead of automatic devices on the much larger transmission pipeline that exploded in San Bruno nearly a year ago.

Capping the lines

Distribution pipes such as the one in Cupertino may not have shutoff valves nearby, PG&E officials say. Often, that means the flow can be stopped only by digging down and capping the line.

Richard Kuprewicz, a pipeline safety consultant, said distribution lines are part of large grids that can be difficult to shut down all at once.

The Cupertino condominium is owned by Lynn Tsui, 45, who had just gone out to lunch with her mother when the explosion happened. Firefighters found her Shih Tzu dog, Tofu, hiding under a bed. The dog was treated for smoke inhalation at a veterinary hospital.

The bedroom was the only part of the condo that did not burn Wednesday, but on Thursday the fire restarted there and destroyed what had survived the initial blast, according to Tsui's family.

Tsui declined to comment, but her brother said a PG&E official had called to tell her that the blast was the company's fault.

"We are fortunate no one got hurt," Wen Tsui said. "My mom and sister are absolutely distraught - they thought Tofu had died."

He said his sister works out of her home as an accountant for a startup. "The damage to her business is very substantial," he said.

Kehmna said it was "very, very fortunate" that Tsui had gone out to lunch. Her dog was lucky as well, he said, but traumatized. "The poor little thing was scared to death."

Leaks repaired

PG&E spokesman David Eisenhauer said the seven gas leaks that crews discovered were at or near a junction where several lines converged. He said he did not know when the lines had been installed.

Eisenhauer said the leaks had been repaired.

"We will investigate this and take corrective actions," he said. "We are going to turn every stone to see what we can determine what happened here."

Nick Stavropoulos, PG&E's executive vice president for gas operations, issued a statement that said, "We are thankful nobody was hurt. We will provide any assistance we can to the residents."

He added, "We will get to the bottom of this as quickly as possible and take any and all necessary corrective actions."

Kehmna said no one had called the county Fire Department to report the smell of gas before the explosion. Eisenhauer said PG&E was trying to determine whether anyone had called the company.

To read and see more stories, photos and videos on PG&E and the San Bruno explosion, click here.