WASHINGTON — (CNN) A federal investigation into the Amtrak 188 derailment that killed eight people and injured more than 200 in Philadelphia last year has concluded that the train’s engineer, Brandon Bostian, was distracted prior to the crash, according to a U.S. official.

Specifically, he was distracted by radio conversations between other trains and dispatchers about other trains being hit with projectiles, the National Transportation Safety Board (NTSB) concluded. It will announce its findings at a public meeting Tuesday in Washington.

NTSB investigators say they found no evidence the Amtrak engineer was using alcohol, drugs or a cell phone.

The ride from the train station in Philadelphia to the site of the derailment was 11 minutes.

Investigators say seven to nine of those minutes the engineer was listening to and participating in the radio conversations regarding other trains being hit with a projectile.

When NTSB investigators interviewed him, the discussion of trains being hit by a projectile was one of the few details the engineer remembered clearly.

NTSB investigators will say there is good circumstantial evidence to make the case that the radio chatter is what distracted Bostian when he approached a 50 mph curve at 106 mph.

The agency will likely make recommendations for recurrent training for train engineers to help them better manage the necessary tasks when in control of a train.

CNN previously reported that the working theory among investigators is that Bostain became distracted by radio chatter from other train operators, and this matches the conclusion reached by the now-completed NTSB investigation.