Mission, TX – Fire officials said Tuesday they believe a corroded underground gas line was to blame for an explosion that destroyed much of a school building.

Nobody was hurt in the blast around dawn Monday at the Sharyland High School field house.

Mission Fire Chief Ricardo Saldana said natural gas leaked out of the corroded pipe, leading to the blast that was centered in the girls locker room.

Authorities are looking into whether the explosion was touched off by lights automatically turning on or the air conditioning kicking in.

The Sharyland school district several days earlier ordered the field house closed after a report of a gas smell in the area.