WASHINGTON (Reuters) - The Pentagon on Friday announced changes to procedures for the cremation of slain U.S. troops after concerns emerged about the military’s use of a crematorium that burns both human and animal remains.

Master Sgt. Richard Estelle plays the trumpet at the Long Island National Cemetery in Farmingdale, New York July 17, 2007. REUTERS/Shannon Stapleton

The changes were unveiled late in the day after Republican presidential candidate John McCain, who sits on the Senate Armed Services Committee, called on the Defense Department for an independent investigation into the cremation of a U.S. soldier due to be buried at Arlington National Cemetery.

“There is no mission more important than the dignified return of our fallen heroes to our families,” Pentagon press secretary Geoff Morrell said.

The crematorium in question was used by the mortuary at Dover Air Force Base in Delaware, where the bodies of troops killed in Iraq, Afghanistan and other overseas locations are returned to the United States, officials said.

In a Friday letter to Defense Secretary Robert Gates, McCain said the Army notified the Senate Armed Services Committee of a report that one soldier’s remains had been cremated at a pet crematorium. The soldier was scheduled to be buried on May 20 at Arlington, across the Potomac River from Washington.

“This report is very disturbing and our men and women in uniform who make the ultimate sacrifice must be treated with dignity,” McCain, a Vietnam War veteran and the Senate committee’s senior Republican, wrote in the letter.

Pentagon officials said the issue came to light after a soldier who works at the Pentagon attended the cremation of a comrade killed in combat and expressed concern about the crematorium. The crematorium is in an industrial area and has a sign advertising the fact that it also cremates pets.

The Pentagon said it had no evidence that the remains of troops had been treated inappropriately at the crematorium.

According to officials, the remains of humans and pets were cremated at separate incinerators at the Delaware crematorium. But officials said Gates believed it was insensitive to cremate the bodies of troops at a site which also cremated animals.

From now on, the military would only use cremation facilities attached to funeral homes, Morrell said.

“The families of the fallen have the secretary’s deepest apology,” Morrell told reporters at the Pentagon.

“Those still serving have his commitment that this department will do everything it possibly can to adhere to the principle that the remains of all members of the armed forces must be treated with the dignity and respect that their sacrifice demands,” he said.

More than 4,070 U.S. troops have died in the Iraq war since U.S.-led forces invaded in March 2003 and nearly 500 have died in the Afghanistan war since U.S.-led forces toppled the Taliban in late 2001.