California fire and utility officials on Tuesday were investigating a natural gas explosion at a home in Murrieta, about 80 miles southeast of downtown Los Angeles that apparently was sparked by a contractor damaging a gas service line.

A Southern California Gas Co. (SoCalGas) service technician on the scene was killed on Monday, and more than a dozen people were injured.

SoCalGas spokesperson Christine Detz said preliminary information indicated the contractor did not call 811 as required to have gas lines marked prior to excavation work.

Three Murrieta firefighters were injured by the blast. A mile-long stretch of the residential community was impacted, and many residents were evacuated from their homes as a precaution.

“We are deeply saddened by today’s incident, which took the life of one of our employees, injured firefighters, and impacted others,” Detz said Monday. “Our employee was responding to reports of a damaged gas line at the home, and our focus has been on working with first responders to make the area safe. We will continue to work with first responders to determine what caused the incident.”