ARLINGTON, Va. >> Families of victims of the deadliest U.S. air disaster since 2001 visited the crash site on Sunday and divers scoured the submerged wreckage for more remains after authorities said they’ve recovered and identified 55 of the 67 people killed.

Washington, D.C. Fire and EMS Chief John Donnelly said officials are confident all will be found. Divers are working diligently to locate remains as crews prepare to lift wreckage from the chilly Potomac River near Reagan National Airport as early as this morning, Donnelly said at a news conference.

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

Donnelly, Pera and other officials spoke hours after dozens of people who lost loved ones in the crash arrived in buses with a police escort to the Potomac River bank near where the two aircraft came to rest after colliding. The jet, en route from Wichita, Kansas, was about to land. The Black Hawk was on a training mission. There were no survivors.

Federal investigators were working to piece together the events that led to the collision.

The National Transportation Safety Board, which is leading the probe, didn’t hold a press briefing on Sunday, but the agency did release a photograph showing investigators on a small boat looking at wreckage and another of them examining a flight data recorder.

Transportation Secretary Sean Duffy on Sunday said he wanted to leave federal investigators space to conduct their inquiry. But he posed a range of questions about the crash while appearing on morning TV news programs.

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 perform an evasive maneuver to avoid the crash.

Full NTSB investigations typically take at least a year, though investigators hope to have a preliminary report within 30 days.