DOVER, Del. — President Obama traveled to Dover Air Force Base on Tuesday to pay his respects to the 30 U.S. troops who were killed Saturday when their Chinook helicopter was shot down in Afghanistan.

According to White House staff accompanying him, Obama was taken in a motorcade down the tarmac to the location of the two C-17s containing the remains of the fallen service members. He was escorted to the planes by Col. Mark Camerer, the 436th Airlift Wing commander. He boarded the planes with his military aide and spent time on board each plane paying his respects.

Beforehand, White House staff said, Obama had been driven to a building on the base where about 250 family members and fellow servicemen and women of the fallen had gathered. He spent approximately 70 minutes in a large community room called The Landings, meeting informally with family members, offering his condolences for their loss and his gratitude for their sacrifice and service.

Other visitors in the room with the family members included Secretary of Defense Leon Panetta; Admiral Mike Mullen, chairman of the Joint Chiefs of Staff; and Admiral William McRaven, head of U.S. Special Operations Command.

Van Williams, public affairs chief for the Dover Air Force Base mortuary affairs operations, said the helicopter crash “was so horrific” that the remains of the servicemen could not be easily identified. They will be identified at Dover by the mortuary team through DNA, dental records and fingerprints.

The bodies, Williams added, were loaded into the plane “all together” in the transportation cases, rather than in the usual single container for each service member.

 Williams said at least three family members for each service member were invited to attend Tuesday’s ceremony, so at least 90 family members were there. Usually, the families stay at the Fisher House, which has nine suites, and they are offered chaplain and mental health services. The president and other military dignitaries would normally pay respects to the families in the Center for the Families of the Fallen, Williams said, but he added that there were so many family members that Dover officials were forced to make alternative arrangements.

After Obama met with the families and visited the C-17s, he and other members of the official party lined up on a red carpet to watch the cases containing the remains removed from the planes in a transfer ceremony, according to a Whiter House official accompanying the president. They saluted as the cases passed, carried by members of various military branches.

 The fallen were first transported from Afghanistan to Ramstein, Germany. The usual procedure is to transport them from Ramstein to Dover on the fastest possible flight, whether that is a military flight or a commercial cargo flight. As is customary, they were transported in flag-draped containers, not burial coffins, he said.

  Mortuary examiners generally try to make a positive identification within three days, Williams said. He added that the large number of bodies should not delay the procedure because more staff can be brought in for the examination.

The services provided at Dover are a “very big source of pride,” Williams said. “There is a sense of duty and honor we give to fallen service members and families. We represent the nation, and a grateful nation at that.”

 After the identifications are made, Williams said, the bodies are dressed in whatever clothing the families have requested for transfer. Some want full military uniforms, others business suits and others T-shirts, jeans and cowboy boots, Williams said.

“We are there for families,” he said. “We don’t tell them what we will give them. They tell us and we accommodate.”

If the remains are too damaged to be clothed, Williams said, the clothes are laid on top.

Pentagon officials continued Tuesday to withhold the identities of those killed in the crash early Saturday in the remote Tangi Valley in eastern Afghanistan.

Family members have revealed to reporters some of the names, but Pentagon officials declined to say why they have not followed suit. “We are not prepared at this time to release the names, that’s all I can tell you,” said Marine Col. David Lapan, a Pentagon spokesman.

The president canceled a scheduled appearance in Northern Virginia to be present for the arrival of the troops’ remains, which was closed to the media. His helicopter landed at the base at 12:30 p.m.

The Defense Department ordinarily makes public the identities of all troops killed in combat in Afghanistan and Iraq. Lapan said that policy remains in place. But most of those killed in the helicopter crash were commandos from the secretive Special Operations Forces, which usually craves anonymity in its work.

Twenty-two of the commandos were Navy SEALs and three were from the Air Force. The other five U.S. casualties aboard were Army aviators. There were also eight Afghans killed in the Chinook crash.

The troops were on a mission to rescue other commandos who had been hunting a Taliban leader in the Tangi Valley but came under fire from insurgents, U.S. military officials have said. The crash is believed to have been caused by an insurgent firing a rocket-propelled grenade as the Chinook tried to land.

The dead included members of Navy SEAL Team Six, the same unit that helped carry out the mission that killed Osama bin Laden in May. None of those killed Saturday were involved in the bin Laden mission.

Obama has visited Dover as president once before, saluting grimly in the pre-dawn darkness as he witnessed the return of 15 soldiers and three Drug Enforcement Administration agents who also were killed in Afghanistan.

Unlike Tuesday’s arrival, family members of the dead were in attendance for the arrival of their remains in October 2009, and a pool of reporters was permitted to witness the ceremony.

In addition to Panetta, Mullen, and McRaven, other Pentagon officials who attended Tuesday’s “dignified transfer” ceremony included: Navy Secretary Ray Mabus; Adm. Gary Roughhead, Chief of Naval Operations; Gen. Peter Chiarelli, vice chief of staff of the Army; Gen. Philip Breedlove, vice chief of staff of the Air Force; Air Force Under Secretary Erin Conaton; Army Secretary John M. McHugh; and Air Force Col. Thomas Joyce.

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This post has been updated since it was first published.