WASHINGTON — President Bush learned of reports that U.S. Marines killed two dozen unarmed Iraqi civilians only after reporters began asking questions, the White House said Tuesday.

Asked when Bush was first briefed about the events in Haditha, an insurgent stronghold in western Iraq, White House press secretary Tony Snow replied Tuesday: "When a Time reporter first made the call."

Frederick Jones, spokesman for the National Security Council at the White House, said Time magazine brought the matter to the attention of the multinational force in Baghdad on Feb. 10. "The questions by Time magazine prompted an inquiry into the Haditha incident and revealed a potential cover-up," Jones said. "The president was briefed soon after the inquiry was opened."

Time magazine was first to report, in March, that the U.S. military was investigating a dozen Marines for possible war crimes in the November incident. The killings, which included women and children, came after a bomb rocked a military convoy on Nov. 19, killing a Marine.

Marines then shot and killed unarmed civilians in a taxi at the scene and went into homes and shot other people, according to Rep. John Murtha, D-Pa., a decorated Marine war veteran and prominent critic of Iraq policy who has talked with military officials.

Bush was briefed on the incident and investigation by his national security adviser, Stephen Hadley, Snow said.

Snow would not detail Bush's personal involvement since.

"I think anybody who's heard the story has a personal interest and it's impossible not to," he said. "But the president also is allowing the chain of command to do what it's supposed to do in the Department of Defense, which is to complete an investigation. The Marines are taking an active and aggressive role in this."

Snow said that he has been assured by the Pentagon that "all the details" will be given to the public once the investigation is over. "We'll have a picture of what happened," Snow said.