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 said yesterday that the cemetery's two civilian leaders would be forced to step aside, and he appointed a new chief 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 is conducted there every day.

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