TX – Fire investigators suspect a natural gas leak caused an explosion at a restaurant before lunch hour in the Rio Grande Valley city of McAllen.

All of the 20 employees and customers taken to the hospital after the blast have been treated and released.

Following the explosion Friday at Palenque Grill, officials at the scene said a gas leak in one of the walls appeared to be the culprit.

Fire investigators have ruled out an intentional attack. But Lieutenant Rene Alaniz of the McAllen Fire Department says it’s too early in the investigation to determine the cause.