DENVER >> An Amtrak worker was seriously injured and two other people suffered minor injuries when a passenger train derailed after it hit a tanker truck carrying milk in northeastern Colorado, authorities said.

The train worker, a 42-year-old man from Utah, suffered injuries in Monday night’s crash that might be life-threatening, Colorado State Patrol spokesperson Sgt. Troy Kessler said Tuesday.

He said a passenger might be among the other two people who were hurt in the crash of the eastbound California Zephyr line, which occurred around 10 p.m. near Keenesburg, a town of about 1,300 people roughly 35 miles (56 kilometers) northeast of Denver.

Amtrak spokesman Marc Magliari said he couldn’t discuss the injured worker’s condition due to privacy reasons.

The truck’s driver, a 31-year-old man from Arkansas, was not taken to the hospital, but Kessler did not know whether he was injured.

The crash is still under investigation but the truck is considered to be at fault, Kessler said. He did not know if the truck was stopped or moving when the train hit it.

There were 69 passengers on the train, which runs between Chicago and the San Francisco Bay area, Amtrak said. All of the passenger cars remained upright.

The tracks where the derailment happened were closed for repairs on Tuesday, preventing the Zephyr from making its full two-day trip, Magliari said. Passengers were being offered refunds or the ability to reschedule their trips.