THE BRONX - The National Transportation Safety Board says a train that derailed in the Bronx was traveling 82 mph as it approached a 30 mph zone.

The Metro-North Railroad commuter train jumped the tracks Sunday morning along a sharp curve near the Spuyten Duyvil station where the speed limit drops from 70 mph to 30 mph. Four passengers died and 63 others were injured while en route to Grand Central Station from Poughkeepsie.

NTSB investigators on Monday mined the train's data recorders, shedding light on preliminary records such as the train's speed and use of its brakes. They say the throttle and brakes were applied too late to stop the train at that speed, and there were no problems with the brakes during the nine stops before the derailment.

Engineer William Rockefeller, who has worked for the Metro-North for 20 years, is being tested for drugs and alcohol, and officials are examining his cellphone.

The NTSB will make recommendations to the Metro-North at the end of its investigation to help prevent another similar incident. The railroad has made some movement toward installing technology that would minimize any human error, but it's delayed anything further until 2018.

The NYPD has also announced that its conducting its own investigation with assistance from the Bronx District Attorney's Office in the event the derailment becomes a criminal case.

The crash claimed the lives of Jim Lovell, 58, of Cold Spring; James Ferrari, 59, of Montrose; Donna Smith, 54, of Newburgh; and Kisook Ahn, 35, of Queens.