Fire officials said they now know what sparked an explosion and fire at a North County pizza restaurant last week.

According to the Carlsbad Fire Department, a gas leak led to the two-alarm blaze that caused more than $1 million in damage to Sammy’s Woodfired Pizza Restaurant located at 5970 Avenida Encinas at about 8 a.m. last Tuesday.

“The investigation uncovered no indication of criminal activity,” said the Carlsbad Fire Department.

The fire has been classified as accidental, according to authorities. A special agent from the Bureau of Alcohol, Tobacco, and Firearms and Explosives assisted Carlsbad fire officials in the investigation.

A Carlsbad police officer first reported the fire. He just happened to be in his car outside the restaurant when the explosion occurred, officials said. The flames were so intense that they could be seen from Interstate 5, causing a traffic backup during the morning commute.

Three employees were in the restaurant at the time. They got out safely.

Company officials said they plan to rebuild at the site.