San Bruno, California (CNN) -- California utility Pacific Gas and Electric will set aside up to $100 million to help rebuild parts of the San Francisco suburb ravaged by a deadly gas explosion last week, the company's president said Monday.
The money includes payments of up to $50,000 per household for interim living expenses and money to compensate the city for San Bruno for the costs it incurred since Thursday night's pipeline explosion and fire, PG&E President Chris Johns told reporters. Other funds will help the city rebuild things like parks and sidewalks, he said.
"I realize money can't return lives, can't heal scars and can't replace memories. Some of the things that have been lost, you can't put a value to," Johns said. "But there does come a time for healing and for rebuilding, and we are committed to helping that happen."
The fire began when a gas transmission line ruptured in San Bruno, near San Francisco International Airport. The blast blew in the doors of a grocery store a quarter-mile (400 meters) away, and the explosion and resulting fire killed at least four people, injured 52 others and destroyed 37 homes.
Another four people remained unaccounted for, according to a news release Sunday from the city of San Bruno, which said two of the previously reported six missing had been located.
In a statement issued by the company, PG&E said the Red Cross and the United Way will help administer its "Rebuild San Bruno Fund." Households can get payments of $15,000, $25,000 or $50,0000, depending on the amount of damage sustained, for costs their insurance policies won't cover and to provide "additional direct immediate financial assistance."
Residents won't won't be asked to waive any claims in exchange for the payments, the company said.
"These funds are being provided in addition to the company's ongoing provision of funds to ensure affected residents continue to have access to temporary housing and other basic necessities," the PG&E statement said.
A 28-foot section of the pipe was blown about 100 feet in the blast, Christopher Hart, vice chairman of the National Transportation Safety Board, told reporters Monday. One end of the pipe was "torn and shredded" after the blast, the cause of which remained under investigation Monday.
The section of pipe that ruptured has been packed up and will be shipped to the NTSB's metallurgy lab in Washington for testing, Hart said. Meanwhile, investigators are nearly finished with their on-site examination of the disaster scene and are now shifting toward a review of documents related to the gas line.
"We're looking at all previous projects that could affect this pipeline," he said.
Investigators have been looking into whether the 30-inch line was damaged when water and sewer lines were laid beneath it, whether it may have been damaged by other digging or even whether a tremor in the notoriously earthquake-prone region weakened the pipe, Hart said.
The pipeline that exploded was laid down in 1948, and some residents have said they called PG&E in the weeks before the explosion to report a smell of gas in the area. Johns said Monday that the company is scouring phone records, "but we have not found anything in our records" that indicates any complaint was filed.
"There is an investigation that will go on, and ultimately it will have its conclusions," Johns said. If that probe lays responsibility with the utility, "We will be accountable for it and we wll make it right," he said.
Most residents of the stricken area were allowed to return Sunday. They gathered in knots on the streets and sidewalks Sunday afternoon as firefighters and investigators poked through the remains of some of the devastated homes.
"I saw all this from the news, but being here the first time coming up here and looking at all this -- no words. I can't really explain," San Bruno resident Walter McCaffrey told CNN.
And his wife, Cherry McCaffrey, said, "It's pretty surreal." She said their home was damaged -- how severely, they weren't sure -- "but the home two doors down is burnt down."
Residents of some badly damaged or destroyed homes or areas where investigators were still working were not allowed to return Sunday.
The pipeline at the heart of the blaze had a "relatively high risk and likelihood of failure," according to a document prepared by PG&E and obtained by CNN. The document recommended the line be replaced, warning that its location in a populated area "makes the risk of a failure at this location unacceptably high."
PG&E officials said Monday the line received its last annual inspection in March.
CNN's Ted Rowlands and Stan Wilson contributed to this report.