U.S. President Barack Obama is honoring the 30 American troops killed in a helicopter crash in Afghanistan.

The president traveled to Dover Air Force Base in the eastern U.S. state of Delaware on Tuesday to pay his respects as the remains of the fallen soldiers, including nearly two dozen elite Navy SEALS, were brought home on two military cargo planes.

Insurgents reportedly shot down the Chinook transport helicopter Saturday, during an anti-Taliban operation in the remote Tangi Valley of Afghanistan's Wardak province. Seven Afghan soldiers and an Afghan interpreter were among the 38 people killed.

The crash is the worst loss of life suffered by U.S. forces in a single incident during the decade-long war in Afghanistan.

Tuesday's arrival ceremony in Delaware was closed to the media because the remains had not been identified. An Air Force official told reporters at the Dover base that the remains were “unidentifiable” because the helicopter crash was “so horrific.”

President Obama's administration lifted an 18-year ban on media coverage of the return of dead soldiers in 2009, leaving the choice up to relatives of those killed.

The White House says President Obama later on Tuesday met with some 250 family and friends of the fallen soldiers who had gathered at the base, and expressed his condolences and gratitude for the troops' sacrifice.

The president did not publicly announce his visit to the air base. He canceled a previously scheduled event in to attend the Dover ceremony.

In Washington Monday, Mr. Obama said the loss of the 30 American troops is “a stark reminder” of the risks that U.S. forces take every day.

NATO says an investigation is under way to determine the exact cause of the helicopter crash.

Violence in Afghanistan is at its worst since the U.S.-led invasion in late 2001, with international troop and Afghan civilian deaths reaching record levels.