LOS ANGELES (AP) — The state’s top rail safety regulator said Monday he would seek an emergency order banning train operators from using cell phones, as federal investigators sought to determine whether the engineer of a commuter train was text messaging before a crash that killed 25 people.

Michael Peevey, president of the California Public Utilities Commission, said some railroad operators have policies prohibiting the personal use of cell phones, but they’re widely ignored. “Our order would make it the law and we’ll go after violators. We owe it to the public,” he said.

The collision on Friday between the Metrolink commuter train and a Union Pacific freight train was the deadliest rail disaster in the U.S. in 15 years. Metrolink has blamed its engineer for not heeding a red light signal designed to prevent such wrecks.

Federal rail investigators said Monday tests at the crash site showed the signals are working properly and there were no obstructions that may have prevented the engineer from seeing the red light.

The National Transportation and Safety Board said it will now review whether engineer Robert Sanchez was text messaging. Investigators did not find a cell phone belonging to Sanchez in the wreckage, but two teenage train buffs who befriended him told KCBS-TV that they received a text message from him a minute before the crash.