SAN FRANCISCO (KGO) -- Federal investigators have released their preliminary report about a gas line explosion in San Francisco on February 6, 2019. The report by the National Transportation Safety Board confirms a third-party contractor working on a telecommunications project damaged a PG&E natural gas main. This released gas, which then ignited.
The report includes a new PG&E photo of the gas main, which has a gaping hole. The report explains how PG&E turned off the gas. It says, "the isolation of the affected segment required turning off six street-level valves located at various points in the area and mechanically squeezing off the 4-inch polyethylene main."
RELATED: A look at the fire, aftermath following gas explosion in San Francisco
The process took close to two and a half hours. The report makes no assessment about whether PG&E's actions were correct or happened quickly enough. It says that will be part of the focus of the investigation going forward. Investigators will also be looking into the third-party contractor's preparedness and qualifications to perform the work.
The gas main was located at the intersection pf Geary Boulevard and Parker Avenue. At the time of the fire, natural gas service to 328 customers was shut off. About 100 people were evacuated. Several buildings were damaged, including the beloved Hong Kong Lounge II. The report says the crews that damaged the pipe only escaped injury because there was about 10 seconds between when the pipe was damaged - which made a noise - and when the gas ignited. This gave them enough time to get further away.
RELATED: Man dining at Hong Kong Lounge II describes terrifying moments after explosion, fire in San Francisco
NTSB investigators were at the scene for several days following the fire. They also sent the damaged portion of pipe to their laboratory in Washington, D.C. for further inspection.
You can read the complete preliminary NTSB report here.
RELATED: Audio captures terror after gas explosion, fire in San Francisco
PG&E released a statement about the report, saying in part: "The NTSB's investigation is ongoing. In the interim, we will continue to support the neighborhood where the third-party dig-in occurred and our customers as they work to repair their homes and businesses. This third-party dig-in serves as a good reminder about the importance of calling the toll free 8-1-1 service ahead of any excavation and following a strict adherence to safe digging practices."
Check out other stories and videos about the Geary gas explosion.