The data recorder that was recovered from the wreckage of last week's NJ Transit crash in Hoboken was not functioning during the trip, and the train's second recorder remains unreachable due to dangerous and precarious conditions at the site.

Thursday's crash killed a woman and injured more than 100 other people. The Hoboken station remains closed and investigators have been unable to reach part of the train due to the heavy damage.

The recovered data recorder was built in 1995. NTSB officials say they have worked with the manufacturer in an attempt to recover information from it, but they could not because it wasn't operational during the trip.

Investigators say they remain hopeful that the second, yet-unrecovered, forward-facing data recorder was working during the crash, and they note that it is likely a newer model.

NTSB officials said at a Sunday news conference on the investigation that they have interviewed both the conductor and engineer of the train.

The engineer is a NJ Transit veteran who was first hired as a ticket collector back in 1987 and eventually became an engineer, officials say. In an interview with authorities, he reported feeling "fully rested" when he arrived to work on the morning of the crash, and said that his cellphone was turned off and stored in a backpack.

The engineer said he was able to conduct a mandatory brake test ahead of departure, and said the train operated normally throughout the trip.

The engineer told investigators that he looked at his watch and recalls arriving at Hoboken about six minutes late, and says he checked the speedometer and saw that he operating at about 10 mph as he entered the station track.

But NTSB officials say the engineer has "no memory" of the crash itself. He remembers waking up on the floor of the cab after the impact.

The conductor told investigators that the train was particularly crowded on the day of the crash, and recalls not being able to collect fares becacuse of the heavy crowding.

Investigators say a curve in the track ahead of the accident area could have supported speeds of up to 43 mph, and the operating rule for the curve is 30 mph.

As the site remains unreachable due to heavy damage and structure instability, investigators say they have used a drone to photograph the area and the collapsed roof of the station. They say it marks the first time that the NTSB has used a drone to document a rail accident.

The new details on the investigation come as a government official revealed that the Federal Railroad Administration found safety violations during an audit in June. According to the official, the audit found more than 150 accidents, which caused more than $4.8 million in damage to tracks or equipment.

New Jersey Transit has reportedly paid more than $500,000 to settle those violations, which ranged from employee drug and alcohol use to violations of railroad operating rules.