WASHINGTON, Feb 2 (Reuters) - Officials have positively

identified 55 of the 67 people killed in Wednesday's midair

collision between an American Airlines ( AAL ) passenger jet and

a military helicopter over the Potomac River in Washington, D.C.

"It's my belief that we're going to recover everyone," Fire

Chief John Donnelly said on Sunday at a press conference. "We

have some work to do as the salvage operation goes on."

On Monday, the Army Corps of Engineers will begin lifting

the wreckage from the river, which officials have said could

take a week or longer.

"We have a wide debris field," said Colonel Francis Pera of

the U.S. Army Corps of Engineers. "Within that wide debris

field, we're employing different techniques to make sure we can

understand what's in the water."

Work will be halted as remains are discovered during removal

operations, officials added.

Earlier on Sunday, relatives of the 67 people killed arrived

at the edge of the river near the crash site on buses.

Wreckage is being moved to a hangar at Washington

Reagan National Airport. Much of the Potomac River remains

restricted to authorized vessels. Two of the lesser-used runways

at the airport remain closed.

Investigators from the National Transportation Safety Board

said Saturday they had determined the CRJ-700 airplane was at

325 feet (99 meters), plus or minus 25 feet, at the time of

impact.

The information was based on data recovered from the jet's

flight data recorder - the "black box" that tracks the

aircraft's movements, speed and other parameters.

The new detail suggests the Army helicopter was flying above

200 feet (61 meters), the maximum altitude for the route it was

using.

Data confirms the air traffic controller alerted the

helicopter to the presence of the CRJ-700 about two minutes

before the crash.

One second before impact, the American flight crew had a

"verbal reaction," according to the plane's cockpit voice

recorder, and flight data shows the plane's nose began to rise,

officials said.