Coalition forces detained four suspects in the Nicholas Berg (search) killing, and two were later released, a U.S. military spokesman said Friday.

The suspects were detained during a raid Wednesday in Baghdad, Brig. Gen. Mark Kimmitt said at a news conference.

Berg's decapitation was captured on a videotape that was released by his killers. His body was found May 8 near a highway overpass in Baghdad. He was last seen on April 10 when he left his Baghdad hotel.

"Coalition forces conducted a raid to capture four individuals suspected of involvement in the Nicholas Berg assassination," Kimmitt said. "Four persons were detained and questioned. Two personnel were released and the other two are still being questioned."

"We may find out that they have no association with the murder but we will continue to question them for some period of time until we are convinced they are innocent," Kimmitt said.

American officials have said they believe Abu Musab al-Zarqawi (search), a Jordanian wanted for allegedly organizing attacks on U.S. troops in Iraq on behalf of Al Qaeda, personally carried out Berg's killing.

Kimmitt said he did not know who the latest suspects were or where they came from.

"I don't know their prior affiliations or prior organizations," he said. "We have some intelligence that would suggest they have knowledge, perhaps some culpability."

Earlier Friday, an Iraqi security official said four people were arrested one week ago in the killing of Berg, and that the group that killed him was led by a relative of Saddam Hussein.

It was unclear whether Kimmitt and the Iraqi security official, who requested anonymity, were referring to different groups of suspects.

The Iraqi official said the suspects were former members of Saddam Hussein's Fedayeen paramilitary organization. Iraqi police arrested them on May 14 in a house in Salaheddin province, north of Baghdad, he said. The province includes Tikrit, Saddam's hometown.

Another Iraqi official confirmed there were arrests in the Berg case, but would not comment further. The official also declined to be named.

The group that was involved in the killing of Berg was led by Yasser al-Sabawi, a nephew of Saddam Hussein, the Iraqi security official said. He said American intelligence had asked Iraqi authorities to hand over the suspects, but they were still in Iraqi hands.

Al-Sabawi was not among those arrested, the Iraqi official said.

A video posted May 11 on an Al Qaeda-linked Web site showed a bound Berg in an orange jumpsuit. He was sitting in front of five men, their faces masked, as one read an anti-American text.

After pushing Berg to the floor, the men severed his head and held it up for the camera. They said his killing was in response to the abuse of Iraqis at Abu Ghraib prison (search).