Washington ? It took nearly a month for President Bush to be told that the military was investigating reports that Marines murdered unarmed civilians in Iraq, the White House said Thursday.

Earlier this week, Bush aides said the president was briefed “soon after” the opening of the probe.

A Time magazine reporter first asked U.S. military officials on Feb. 10 about the circumstances surrounding the alleged massacre on Nov. 19, in which 24 people in Haditha, an insurgent stronghold in western Iraq, were killed following a bomb attack on a military convoy in which a Marine died. Four days later, on Feb. 14, Lt. Gen. Peter Chiarelli, commander of Multinational Corps Iraq, ordered an investigation into the incident, White House press secretary Tony Snow said Thursday.

But, Snow said, Bush was not informed about the investigation until March 11, when he was briefed by national security adviser Stephen Hadley.

Bush pledged Thursday that the Pentagon will “get to the bottom of this” and that the results of the inquiry will be made public.

“The world will see the full and complete investigation,” he said after meeting with his Cabinet at the White House. “If there is wrongdoing, people will be held to account.”

A senior defense official said last week that military investigators have evidence that points toward unprovoked murders by Marines.

Snow said the president had not commented publicly until this week because he had not been asked about the incident sooner, and that was the appropriate way for it to be handled by the commander in chief. Responding to a question on Wednesday, Bush said he was troubled by the reports and promised that anyone who broke the law would be punished.