ARLINGTON, Va. — Salvage crews have recovered an engine and large pieces of fuselage and are working to retrieve a wing from the wreckage of a commercial airliner involved in last week’s midair collision near Ronald Reagan Washington National Airport, officials said Monday.

They also recovered more human remains from the Potomac River, although they declined to offer specifics, reiterating only that 55 of the 67 victims have been found and identified since the crash Wednesday evening.

Authorities have said the operation to remove the plane will take several days, and they will then work to remove the military helicopter involved in the crash.

The crash over Washington was the deadliest U.S. air disaster since 2001.

Washington Fire Department Assistant Chief Gary Steen told a news briefing that officials are confident all of the victims would be found. More than 300 responders are taking part in the recovery effort, officials said. Two Navy barges were also deployed to lift heavy wreckage.

Divers and salvage workers are adhering to strict protocols and will stop moving debris if a body is found, Col. Francis Pera of the Army Corps of Engineers said Sunday. The “dignified recovery” of remains takes precedence over all else, he said.

Portions of the two aircraft that collided over the river — an American Airlines jet with 64 people aboard and an Army Black Hawk helicopter with three soldiers aboard — are being loaded onto flatbed trucks and will be taken to a hangar for investigation.

The crash occurred when the jet, en route from Wichita, Kansas, was about to land. The Black Hawk was on a training mission.

The plane’s passengers included figure skaters returning from the 2025 U.S. Figure Skating Championships in Wichita and a group of hunters returning from a guided trip.

Federal investigators were working to piece together the events that led to the collision. Full investigations typically take a year or more. Investigators hope to have a preliminary report within 30 days.

Wednesday’s crash was the deadliest in the U.S. since Nov. 12, 2001, when a jet slammed into a New York City neighborhood just after takeoff, killing all 260 people on board and five on the ground.

Experts stress that plane travel is safe, but crowded airspace around Reagan National can challenge even experienced pilots.

The NTSB said Saturday that preliminary data showed conflicting readings about the altitudes of the airliner and the helicopter.

Investigators also said that about a second before impact, the jet’s flight recorder showed a change in its pitch. But they did not say whether that change in angle meant that pilots were trying to avoid the crash.

Data from the jet’s flight recorder showed its altitude as 325 feet, plus or minus 25 feet, when the crash happened, NTSB officials told reporters.

Data in the control tower, though, showed the Black Hawk at 200 feet, the maximum allowed altitude for helicopters in the area.