Documents obtained by The Associated Press showed that Pacific Gas & Electric submitted paperwork to regulators that said a section of the same gas line -- about two and half miles from the blast -- was within "the top 100 highest risk line sections" in the utility's service territory.

The federal Pipeline and Hazardous Materials Safety Administration classified the 30-inch diameter transmission line as a "high consequence area" requiring more stringent inspections called integrity assessments, agency spokeswoman Julia Valentine said.

Nationwide, only about 7 percent of gas lines have that classification, she said.

The official death toll from the blast was four Sunday, and San Mateo County Coroner Robert Foucrault said they're still trying to confirm whether more remains found are human and identify victims. Police have said five people are missing.