A U.S. soldier was missing Friday, a day after a suicide truck bombing killed two soldiers and wounded another 30 west of Baghdad, U.S. military officials said.

The news came as the military said a U.S. Marine was killed Friday in Anbar province and an American soldier was killed Thursday evening by a roadside bomb northwest of Baghdad bringing that day's count to five servicemen killed.

The missing soldier was "reported as Duty Status Whereabouts Unknown," the military said, without elaborating.

U.S. military officials in Iraq and Washington would not say whether they believed the soldier had been abducted or whether he may have been killed in the attack, and his remains had not been recovered.

"I'm sorry to add that we now have a soldier that we are counting as missing," Lt. Gen. Peter Chiarelli said in a video news conference from Baghdad with reporters at the Pentagon.

The attack occurred Thursday, when a truck driven by a suicide bomber exploded near an Iraqi power substation about 12 miles west of Baghdad, in an area where the U.S. troops were.

The soldiers had been guarding the power substation, U.S. military spokesman Lt. Col. Barry Johnson said, adding that the blast occurred near concrete barriers, causing debris and shrapnel to be scattered across the area and inflicting many of the wounds.

Johnson could not comment on what type of explosives were used, whether there was more than one suicide bomber or whether the U.S. soldiers took any action against the vehicle before it exploded.

"The whole incident remains under investigation to determine how this happened and why," Johnson said.

Of those wounded in the attack, one was listed as very seriously injured and one as seriously injured, the military statement said. Eleven returned to duty, and 17 were slightly wounded, it said.

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