SAN BRUNO, CALIF. ? The section of gas pipeline that ruptured and exploded in a suburban San Francisco neighborhood, killing at least seven and injuring nearly 60 others, was ranked as high risk because it ran through a highly populated area, state and federal authorities said Saturday.

One of the victims killed in the inferno Thursday worked for the commission reviewing Pacific Gas & Electric’s investment plans to upgrade its natural gas lines, including another risky section of the same pipeline within miles of her home, a colleague confirmed.

Longtime California Public Utilities Commission analyst Jacqueline Greig and her 13-year-old daughter Janessa died in the massive blast, which left a crater near their house and laid waste to dozens of 1960s-era homes in the hills overlooking San Francisco Bay.

Jessica Morales, 20, was also killed in the explosion and fire. One other victim found earlier hasn’t been identified, and authorities were trying to identify remains found Saturday morning.

Six people were still missing from the blast, officials said Saturday night.

Greig spent part of the summer evaluating PG&E’s expansion plans and investment proposals to replace out-of-date pipes, co-worker Pearlie Sabino said.

Sabino and Greig were members of a small commission team that advocates for consumer and environmental protections pertaining to natural gas.

“It’s just so shocking because she was one of the ones who was most closely involved with this kind of work,” said Mike Florio, an attorney with a San Francisco-based utility reform advocacy group who worked with Greig.

Among the paperwork PG&E submitted for gas rate proceedings with regulators was a document ranking a section of the same gas line about two and half miles from the blast as within “the top 100 highest risk line sections” in the utility’s entire service territory, documents show.

PG&E did not immediately respond to a request for comment Saturday and referred questions related to the investigation to federal authorities.

The federal Pipeline and Hazardous Materials Safety Administration classified the 30-inch diameter transmission line, which ran for about a mile and a half near Greig’s home, 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 state commission gave that section of pipe the same classification and had conducted audits on that stretch, spokeswoman Terrie Prosper said. PG&E also had conducted leak surveys, evaluations and patrols on the gas line, she said.

Reams of data and records have been requested from PG&E, National Transportation Safety Board vice chairman Christopher Hart said at a Saturday evening briefing.

The segment of pipe that blew out onto the street was 28 feet long, and the explosion sent that piece of pipe about 100 feet, he said. The blast created a crater 167 feet long and 26 feet wide.