The Air Force says at least two crew members are dead after the crash of a B-52 bomber off Guam.

Rescue teams are searching a vast area of the Pacific Ocean on Monday for the remaining four airmen.

The Coast Guard says six vessels, three helicopters, two F-15 fighter jets and a B-52 bomber are involved in the search.

The military says the B-52 was en route to a flyover in a parade when it crashed about 9:45 a.m. about 30 miles northwest of Apra Harbor. The plane was based at Barksdale Air Force Base in Louisiana.

THIS IS A BREAKING NEWS UPDATE. Check back soon for further information. AP's earlier story is below.

HONOLULU (AP) — Rescue crews were searching a vast area of floating debris and a sheen of oil Monday for crew members of an Air Force B-52 bomber that crashed off the island of Guam, officials said.

At least two people from the bomber's six-man crew were recovered from the waters, but their condition was not immediately available, the Coast Guard said.

Maj. Stuart Upton, a Pentagon spokesman, said the aircraft was unarmed.

Six vessels, three helicopters, two F-15 fighter jets and a B-52 bomber were involved in the search, which had covered about 70 square miles of ocean, said Coast Guard spokeswoman Lt. Elizabeth Buendia.

"We have an active search that's going to go on throughout the night," she said Monday. The Navy, Coast Guard, Air Force and local fire and police departments were involved.

The B-52 bomber based at Barksdale Air Force Base in Louisiana was en route to conduct a flyover in a parade when it crashed around 9:45 a.m. Monday about 30 miles northwest of Apra Harbor, the Air Force said.

The Liberation Day parade celebrates the day when the U.S. military arrived on Guam to retake control of the island from Japan.

The Air Force said a board of officers will investigate the accident.

The accident is the second for the Air Force this year on Guam, a U.S. territory 3,700 miles southwest of Hawaii.

In February, a B-2 crashed at Andersen Air Force Base shortly after takeoff in the first-ever crash of a stealth bomber. Both pilots ejected safely. The military estimated the cost of the loss of the aircraft at $1.4 billion.

The B-52 is a long-range, heavy bomber that can refuel in mid air. Since the 159 foot-long bomber was first placed into service in 1955, it has been used for a wide range of missions from attacks to ocean surveillance. Two B-52s, in two hours, can monitor 140,000 square miles of ocean surface.

According to the Air Force's Web site, the B-52 Stratofortress has been the backbone of the manned strategic bomber force for the United States for more than four decades. It is capable of dropping or launching the widest array of weapons in the U.S. inventory, including cluster bombs and precision guided missiles.