Federal investigators in the California train collision that killed 25 passengers and injured 130 more last week are trying to obtain phone records that could help them establish the cause of the terrible accident.

According to the most recent reports, one minute before the collision, the engineer responsible for the crash sent a text message from his cell phone, apparently just one of several messages that had been exchanged between him and two teenagers before the disaster.

The National Transportation Safety Board has reportedly contacted the two 14-year-old boys, who’ve admitted exchanging text messages with the train engineer. Although the name of the engineer has not been made public, he is believed to be responsible for the accident, which resulted in 25 fatalities, including him.

Kitty Higgins, member of the National Transportation Safety Board, said train operators are not allowed to use cell phones while on duty. Unfortunately, the investigators are taking small steps towards establishing the details of the accident, due to the fact that they have not been able to recover the engineer’s cell phone from the crash site.

However, the preliminary investigation revealed that the train engineer ignored the red signal that indicated the approach of another train, which makes him responsible for the collision. According to NTSB, a dispatcher tried to warn the engineer about the imminent collision, however it was too late.

The investigators are hoping that once they’ll obtain the engineer’s phone records and cell phone, they will be able to learn more about what happened, Furthermore, they said they are looking into multiple factors that might have caused the collision, in addition to the engineer’s lack of responsibility at the time.