The contractor, Connex Railroad, provides the engineers who run Metrolink trains.

Investigators have said the Metrolink train went through a red signal and its engineer had repeatedly sent text messages on duty that day — one just seconds before the impact that killed 25 people.

Rail authority board Vice Chairman Keith Millhouse says the suit was filed Thursday in federal court. He declined to comment further on it.

A Connex spokeswoman says she hasn't seen the lawsuit.