SAN BRUNO, Calif. — Federal authorities are probing a natural gas pipeline and how it was maintained as they investigate the thunderous line explosion and raging inferno that devastated this suburban San Francisco neighborhood.

City leaders called for a town-hall meeting today to start San Bruno's healing process.

Officials were trying to determine what led up to the blast that killed at least four people, injured dozens of others and raised questions about the safety of similar lines that crisscross towns across America.

"It looks like a moonscape in some areas," Fire Chief Dennis Haag said Friday.

At least 50 people were hurt, with seven suffering critical injuries in the explosion Thursday evening that left a giant crater and laid waste to dozens of 1960s-era homes in the hills overlooking San Francisco Bay. Authorities had no reports of anyone unaccounted for.

The utility that operates the 30-inch diameter line said it was trying to find out what caused the steel gas pipe to rupture and ignite. Federal pipeline safety inspectors were on the scene Friday.

Federal investigators will analyze the pipeline's condition, along with its maintenance history, pressure levels and the safeguards put in place to prevent pressure from building up.

By The Associated Press