Manchester, MO- JEFFERSON CITY, Mo. (AP)- An explosion that leveled a suburban St. Louis home last year, injuring four people, was caused by natural gas escaping from a service line to the home, staff of the Missouri Public Service Commission said Wednesday.

The gas escaped because a service line pulled out of a connection at the gas main. The gas migrated into the house, ignited and exploded, said Bob Leonberger, a gas safety and engineering manager at the Missouri Public

Service Commission.

No one died in the explosion about 6:20 a.m. Dec. 11 near Big Bend Road and Highway 141 in west St. Louis County. The blast left virtually nothing but debris at the site of the house, and the initial theory from firefighters had pointed to natural gas.

The report said a joint in the service line was not assembled properly when installed 30 years ago. Since then, tree roots put pressure on the line, forcing a pullout.

The Public Service Commission filed a complaint against Laclede Gas Co. alleging it violated a regulation for proper assembly of plastic pipe mechanical joints. The commission’s staff has asked the agency to go to circuit court to seek penalties against Laclede Gas.

The force of the explosion triggered a fire that damaged houses on either side of the home that was destroyed. Firefighters temporarily

evacuated about 25 homes when crews detected natural gas in the sewers.

Laclede Gas spokesman George Csolak said Wednesday the event was an isolated incident, and that the company will work “consistently and proactively to address the commission staff’s recommendations.”