U.S. troops have detained at least two Iraqis suspected of involvement in last week's crash of a Black Hawk (search) helicopter believed shot down, an officer said Thursday.

The two Iraqis were arrested during raids Tuesday night in Tikrit (search) by the 10th Cavalry Regiment of the 4th Infantry Division (search) and were being interrogated, Lt. Col. Steven Russell said.

The Black Hawk crashed Friday on a field near the eastern bank of the Tigris River. All six Americans aboard were killed.

The U.S. military has not released an official finding of what caused the crash, but the commander of U.S. forces in Iraq, Lt. Gen. Ricardo Sanchez, said he believed the helicopter was shot down.

It was unclear to what extent the suspects arrested Tuesday may have been involved in the incident. However, Russell said U.S. officers are "obviously satisfied that the people we've detained have some connection to the incident or we would not have gone after them."

"We still have some important leads we're trying to follow," he added without elaborating.

Hamid Muzhir, the police chief of Salahuddin province that includes Tikrit, said he believed the Black Hawk was downed by members of Saddam Hussein's security forces and not ordinary Tikrit residents opposing American presence in Iraq because of the considerable training needed to launch an attack.

On Wednesday, American troops detained two Iraqis who were caught planting a homemade bomb near a U.S. civil military operations center in Samara, said Maj. Josslyn Aberle, a spokeswoman of the 4th Infantry Division.