KABUL, Afghanistan - International military forces worked on Monday to recover every last piece of a Chinook helicopter that crashed over the weekend, killing 30 American troops, seven Afghan soldiers and an Afghan interpreter, NATO said.
Plans were in place for the fallen U.S. troops' bodies to be flown home to American soil on Tuesday morning aboard a military plane destined for Dover Air Force Base in Delaware.
The technical repatriation of the troops' remains was to take place at the U.S. Bagram Air Force Base in Afghanistan later Monday, a military source tells CBS News.
German Brig. Gen. Carsten Jacobson, a spokesman for the U.S.-led coalition, told reporters that troops had secured the crash site in a rugged area of eastern Wardak province and nobody was being allowed in or out of the area while the investigation was ongoing.
Jacobson said the coalition still had not yet determined the exact cause of the crash, but some officials have said the heavy and lumbering transport helicopter was apparently shot down. Officials said the helicopter was hit as it was flying in and approaching the area.
"We are still investigating this incident so we have no picture of what was the cause for the incident. That is what the investigation is basically all about," Jacobson said.
The helicopter was ferrying a group of U.S. Navy SEALs to reinforce a group of U.S. Army Rangers who were under fire. It remains unclear if the Rangers and SEALs were taking part in a night raid to capture or kill an insurgent leader.
It was deadliest single incident for U.S. forces in the decade-long war.
CBS News national security correspondent David Martin reports the Chinook was hit by what is believed to have been a rocket propelled grenade after rushing to assist Army Rangers who called for help after hitting the compound of a local Taliban leader.
Of the 30 Americans aboard, Martin reports that 22 were members of the Special Operations Navy Seal Team Six - the same unit that killed Osama bin Laden.
The other eight were Army and Air Force personnel.
U.S. defense officials have not officially released the names of those killed, but Martin reports word has been spreading as the friends and family mourn their losses.
Many of the fallen troops were still in their 20s and 30s - some of them with young children.
Martin reports that a change of command ceremony planned for Monday at SEAL headquarters in Miami was to go ahead, but it would take on a distinctly different air from the original plans, becoming a solemn occasion rather than a celebration.
Meanwhile, another NATO helicopter made a hard landing Monday in eastern Paktia province, the U.S.-led coalition said. It did not report any casualties and said the cause of the hard landing was under investigation. The coalition said there was no enemy activity in the area at the time.
The helicopter was a CH-47 of the same type that crashed on Saturday. It was flying in to pick up special operations troops, but apparently suffered a mechanical failure and crash-landed, an officer in the war zone said. He could not be named because he was not authorized to comment publicly. The crew was rescued by the troops.
The fatal crash on Saturday highlights the risks confronting the U.S.-led coalition as it looks to rely more on special operations forces while reducing the overall number of troops in Afghanistan by the end of 2014.