Honor Guard members stand in formation beside the Tomb of the Unknowns in Arlington National Cemetery in Arlington, Va., in this Nov. 11, 2007, file photo.

Washington ? An Army investigation has found that potentially hundreds of remains at Arlington National Cemetery have been misidentified or misplaced, in a scandal marring the reputation of the nation’s pre-eminent burial ground for its honored dead since the Civil War.

Army Secretary John McHugh announced Thursday that the cemetery’s two civilian leaders would be forced to step aside, and he appointed a new chief to conduct a more thorough investigation to examine the graves and sort out the mix-up.

“I deeply apologize to the families of the honored fallen resting in that hallowed ground who may now question the care afforded to their loved ones,” McHugh told a Pentagon news conference.

Arlington National Cemetery is considered among the nation’s most hallowed burial sites, with more than 300,000 people buried there with military honors. An average of 30 funerals are conducted there every day.

Among those buried at the cemetery are troops killed in Iraq and Afghanistan, as well as service members from past conflicts dating back to the Civil War.

Famous presidents and their spouses, including members of the Kennedy family, also have been buried there. The cemetery, located across the Potomac River from Washington in northern Virginia, attracts more than 4 million visitors annually.

An Army investigation was launched last year after reports of employee misconduct, first reported by website Salon.com.

Led by the service’s inspector general, Lt. Gen. Steven Whitcomb, the investigation found lax management of the cemetery, where employees relied on paper records to manage the dozens of burials each week and maintain the thousands of existing gravesites.

Whitcomb said at least 211 remains were identified as potentially mislabeled or misplaced and that there could be more.

“We found nothing that was intentional, criminal intent or intended sloppiness that caused this. … But of all the things in the world, we see this as a zero defect operation,” he told reporters Thursday.

Whitcomb could not say how old the mixed-up remains might be or from what conflict, saying only that the problem had been confined to three areas of the cemetery known as sections 59, 65 and 66.

Whitcomb said he did find two cases of mis-marked graves in section 60, the area for veterans from Iraq and Afghanistan. He said those mistakes had been corrected.

Dorothy Nolte, 68, of Burns, Tenn., said she learned last year that the remains of her sister, Air Force Master Sgt. Marion Grabe, who had been buried at Arlington in March 2008, had been moved to a new grave site. Nolte said she went to Arlington to find out that her sister’s urn had been buried on top of another soldier, but then it was disinterred and moved to another grave site. She said she had not been informed of the transfer.

“I made them unearth the urn so I could see the name,” Nolte said in a phone interview Thursday from New York. “I have peace knowing my sister is indeed in the right place.”