HELENA, Mont. (AP) — A preliminary report on the derailment of an Amtrak train in north-central Montana last month that killed three people and injured dozens more gave no information on the cause of the accident, but said the train’s emergency brakes were activated and that Amtrak estimated the damage at $22 million.

The National Transportation Safety Board’s report issued Tuesday said the westbound Empire Builder was carrying 154 people when it derailed Sept. 25 just west of Joplin, Montana. A total of 44 passengers and crew were taken to local hospitals with injuries, the report said.

The train was traveling at between 75 and 78 mph, just below the speed limit of 79 mph on that section of track when its emergency brakes were activated.

The two locomotives and two railcars remained on the rails and eight cars derailed.

NTSB spokesman Keith Holloway said Tuesday that it was “still very early” in the investigation and the agency typically takes one to two years to determine accident causes.

“We are looking at everything,” he said.

Rail experts have said the crash could have been caused by problems with the railroad or track, such as a rail that buckled under high heat, or the track itself giving way when the train passed over.

But they said investigators would consider all possibilities, including potential problems with the Empire Builder’s wheels or suspension system. Investigators also were examining if passengers were ejected from the train during the crash.

Survivors described horrific scenes of people being maimed and killed as four cars — including an observation car with large windows — toppled and skidded down the tracks.

Killed in the accident were Margie and Don Vardahoe, a Georgia couple on a cross-country trip to mark their 50th wedding anniversary, and Zachariah Schneider, 28, a software developer from Illinois.

At least two dozen passengers have filed lawsuits over the derailment, including one by Schneider’s wife, Rebecca Schneider. She said in the lawsuit that her husband had left her in the sleeping car and went to sit in the viewing car, where he was “horrifically maimed” and killed. The viewing car was one of four passenger cars that ended up on their sides.

The lawsuits against both Amtrak and BNSF allege negligence for not preventing the derailment. The suits seek damages for injuries and psychological trauma to the people aboard the train.

Amtrak and BNSF have declined to comment on ongoing litigation.

The lawsuits also challenge a mandatory arbitration agreement Amtrak put in effect in January 2019, which attorneys for the victims say denies passengers their constitutional right to a trial by jury if they are injured and sets a maximum of $295 million in damages per incident.