(CNN) One person is dead and 15 more are injured, after a house in Murrieta, California, exploded Monday afternoon.

Crews from the Southern California Gas Company (SoCalGas) were at the home fixing a natural gas line that was reported damaged by a contractor working on the house. The explosion occurred about an hour after the crew arrived, and the fire department was already on the scene.

The deceased was confirmed to be an employee of SoCalGas. The 15 injured are being treated. Three of the injured are firefighters, Murrieta Fire and Rescue Deputy Chief David Lantzer told reporters Monday night. He did not provide details about the severity of the others' injuries.

"We are deeply saddened to learn of today's incident which took the life of one of our employees, injured firefighters, and impacted others," SoCalGas said in a statement. "Our focus now is on working with first responders to make the area safe, and supporting all those involved. We will continue to work with first responders to determine what caused the accident. Our sympathies and thoughts are with the individuals and families of those impacted."

Cedric Williams, SoCalGas vice president of construction, said a preliminary investigation showed that the contractor did not call 811 before digging, as the law mandates contractors to do. Williams also said there was not an open ticket for the contractor's work.

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