WASHINGTON (AP) – It took nearly a month for President Bush to be told that the military was investigating reports that Marines killed 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 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.

Snow said the president must be careful to remain “out of the chain of command.”

“You’ve got ongoing criminal inquiries on two tracks: facts on the ground and the reporting,” Snow said. “If the commander in chief says anything that might be regarded as prejudicial to proceedings, those who are conducting the inquiries and those who might be called upon to conduct trials are therefore going to be hamstrung.”

Said Bush: “I’m not involved with the investigation, and you shouldn’t expect me to be. I expect this investigation to be conducted independent of the White House, with a full and thorough investigation.”

According to a timeline provided by Snow, a preliminary report on March 3 recommended additional inquiry. Chiarelli received initial findings from that on March 9 and asked for the further review that still is ongoing. Defense Secretary Donald H. Rumsfeld and Gen. Peter Pace, chairman of the Joint Chiefs of Staff, were informed the next day and Bush the day after, on a Saturday.

Time reported the investigation on March 19.

The Iraqi government is conducting its own inquiry, in addition to at least two separate investigations by the U.S. military. Those include a probe into why the American military’s initial statement about the incident described it as an ambush on a joint U.S.-Iraqi patrol, with a roadside bombing and subsequent firefight killing 15 civilians, eight insurgents and a Marine. The statement, which said the 15 civilians were killed by the blast, has led some to allege a cover-up.

The president said the ethical training ordered for U.S. troops in Iraq came as a result of the Haditha incident.

“This is just a reminder – for troops in Iraq or throughout our military – that there are high standards expected of them and that there are strong rules of engagement,” said Bush, who said he has spoken to Pace about the matter several times.