The US military is trying to confirm whether insurgent fire brought down a helicopter in Afghanistan with the loss of 38 people, most of them Americans.
The dead included Navy Seals, Afghan commandos, US Air Force personnel, a dog handler, the Chinook crew and a civilian interpreter.
The 30 US deaths are the largest single American loss of life in the conflict.
On Sunday another four Nato soldiers were killed in two separate attacks in Afghanistan.
France has confirmed that two of its soldiers were among the dead - they were killed during an operation in the Tagab valley in Kapisa province, north-east of Kabul, President Nicolas Sarkozy's office said in a statement. Five other French soldiers were injured.
Nato has not confirmed the nationality of the other two soldiers but said they were killed in an attack in the south.
Bin Laden unit
The Chinook helicopter went down in a district of Wardak province, west of Kabul, early on Saturday.
Officials, witnesses and the Taliban have said it was shot down by insurgents during a combat mission.
The presence of at least 17 of the Seals has led to speculation that they were involved in a highly significant operation, such as targeting a high-ranking figure in the insurgency.
US sources have said they were from the same Navy Seal unit, known as Team Six, which killed Osama Bin Laden in May, but are "unlikely" to be the same personnel.
American officials have refused to confirm the cause of the crash on the record but some have told news agencies they believe the Chinook was shot down.
Afghan officials in Wardak province said a Taliban rocket hit the craft. A local resident who saw the incident told the BBC that he saw the Chinook catch fire and crash after a rocket hit it.
The Taliban claimed they shot the helicopter down as it was involved in a raid on a house in Wardak where insurgents were gathering.
The BBC's Quentin Sommerville in Kabul says it is rare for the Taliban to shoot down aircraft.
The Taliban say they have modified their rocket-propelled grenades to improve their accuracy but that may not be true, our correspondent says.
The top US military officer, Adm Mike Mullen, said it was too soon to say what brought it down.
"Information is still coming in about this incident. I think it's important that we allow investigators to do their work before jumping to too many conclusions," the chairman of the Joint Chiefs of Staff said.
President Barack Obama paid his condolences to the Americans and Afghans killed in the crash.
"Their deaths are a reminder of the extraordinary sacrifices made by the men and women of our military and their families, including all who have served in Afghanistan," he said in a statement on Saturday.
The US is relying more on special forces to fight the war against insurgents in Afghanistan, carrying out night raids against key leaders and conducting surveillance operations.
After last year's increase in troop numbers - credited with some success in reducing Taliban activity in southern Afghanistan - some withdrawals have begun. The goal is for all foreign combat forces to leave the country by the end of 2014.
There are currently about 140,000 foreign troops - about 100,000 of them American - in Afghanistan, fighting the Taliban insurgency and training local troops to take over security.
The Nato-led International Security Assistance Force has begun the process of handing over control of security in some areas to local forces. Bamiyan became the first province to pass to Afghan control in mid-July.