LOS ANGELES—Federal regulators issued an emergency order Thursday banning use of cell phones and other electronic devices by rail workers, a day after investigators said a commuter-train engineer was text messaging moments before a deadly crash last month.

Violators could be fined or removed from their jobs under the Federal Railroad Administration rule, which comes as the National Transportation Safety Board investigates why Metrolink engineer Robert Sanchez ran through a red light and into a freight train, killing 25 people.

Preliminary evidence released Wednesday by the NTSB on the timing of the messages appears to rule out that he was unconscious at the time and could show that Sanchez, who was among the dead, was distracted at the time of the crash, experts said. “They know what’s probable, that he was distracted while sending a text message or getting ready to send one,” said Ron Schleede, who retired from the NTSB after 28 years as an accident investigator. “He was not incapacitated, but he was also not alert and paying attention.”

NTSB investigators have found no indication of mechanical error, signal malfunction or problems with the track. While the NTSB has not made a finding about the cause of the crash, Metrolink has already said Sanchez went through the stop light.

An NTSB spokeswoman would not comment further Thursday about the investigation, which could take more than a year.

In issuing the order, the Railroad Administration noted that rail workers are increasingly using cell phones and other electronic devices that could distract them at critical moments during railroad operations. It noted six train accidents, four of them resulting in deaths, between 2000 and 2006 in which cell phone use was involved.

“These obviously unsafe practices reflect the powerful influence of pervasive use of cell phones and other electronic and electrical devices,” the report said.

While most railroads prohibit or restrict use of electronic devices by rail workers on duty, the Railroad Administration said the rules have not proved effective in preventing train accidents.

Wireless phones provide an extra means of communication among engineers, conductors and dispatchers in the event of a radio failure, but Metrolink decided to prohibit cell phones outright in the locomotive cabin, said Keith Millhouse, vice chairman of the regional rail system’s board of director.

“When we adopted this policy some time ago about the need for a communication backup, it was decided the benefits of not having it in the cab outweigh the benefits of having it,” Millhouse said. The board decided to allow the conductor, who collects fares, announces stops and performs other duties in the cars, to carry a cell phone in case radio communication went out, he said.

Sanchez’s cell phone records show he sent a text message 22 seconds before the Metrolink train crashed head-on into a Union Pacific train Sept. 12 on a curve in the San Fernando Valley community of Chatsworth. In all, he sent and received 57 messages while on duty that day.