Baghdad, Iraq ? Residents gave new details Monday about the shootings of civilians in a western Iraqi town, where the U.S. military is investigating allegations of potential misconduct by American troops last November.

The residents said troops entered homes and shot and killed 15 members of two families, including a 3-year-old girl, after a roadside bomb killed a U.S. Marine.

The military, which announced Friday that a dozen Marines are under investigation for possible war crimes in the Nov. 19 incident, said in a statement Monday that a videotape of the aftermath of the shootings in Haditha, 140 miles northwest of Baghdad, was presented in support of the allegations.

The charges against the Marines were first brought forward by Time magazine, which reported this week that it obtained a videotape two months ago taken by a Haditha journalism student that shows the dead still in their nightclothes.

The magazine report mirrored what was told independently to The Associated Press by residents who described what happened as “a massacre.” However, Time said the available evidence did not prove conclusively that the Marines deliberately killed innocents.

A military spokeswoman said Monday the allegations were being taken “very seriously.”

Khaled Ahmed Rsayef, whose brother and six other relatives were killed, said the roadside bomb exploded about 7:15 a.m. in the al-Subhani neighborhood, heavily damaging a U.S. Humvee.

A U.S. military statement in November described it as an ambush on a joint U.S.-Iraqi patrol that left 15 civilians, eight insurgents and a U.S. Marine dead in the bombing and a subsequent firefight.

The statement said the 15 civilians were killed by the blast, a claim that residents denied.

The residents said the only shooting done after the bombing was by U.S. forces.

“American troops immediately cordoned off the area and raided two nearby houses, shooting at everyone inside,” said Rsayef, who did not witness the events but whose 15-year-old niece says she did. The girl survived by pretending to be dead.

Seven people were killed in the first house, including one man who burned to death after a grenade was thrown into his room. Eight people were shot and killed in the second house, including Rsayef’s brother Younis. Victims ranged in age from 3 to 76 years old.

“It was a massacre in every sense of the word,” Rsayef said.

Rsayef and another resident, former city councilman Imad Jawad Hamza, who spoke with hospital officials and residents, said the troops also shot and killed four brothers who were walking in the street, then shot dead five men who were in a car near the scene.

It was not clear whether the nine men were involved in the attack as the military statement said.