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 the National Transportation Safety Board.

Specifically, he was distracted by radio conversations between other trains and dispatchers about other trains being hit with projectiles, the NTSB concluded, announcing their 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.

READ: Driver: ‘I don’t remember anything’ before crash

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 said 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 board made recommendations to the Federal Railroad Administration Tuesday for recurrent training for train engineers to help them better manage the necessary tasks when in control of a train.

The board wants to require that railroads install devices and develop procedures that will help crewmembers identify their current location as well as display their upcoming route in territories where positive train control will not be implemented.

The board also recommended that Amtrak incorporate strategies into their initial and recurrent training for operating crewmembers for recognizing and effectively managing multiple concurrent tasks in prolonged as well as atypical situations to sustain their attention on current and upcoming train operations.

The board recommended that the Philadelphia police and fire departments collaborate and develop a plan that effectively integrates rapid police transport of patients into the emergency medical response plans for large mass casualty incidents. The plan should also include a means of coordinating hospital destinations regardless of the method of transport.

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.

CNN’s Eugene Scott contributed to this report.