A truck driving toward a Baghdad (search) police station plowed into a bus just before dawn Wednesday, killing at least 10 Iraqis.

Earlier reports said the cause of the explosion was a truck bomb, but Capt. Jason Beck of the 1st Armored Division's headquarters in Baghdad told Fox News that the explosion was caused by a crash between a fuel truck and a bus.

"Our investigation on the scene of the accident indicates that the truck was not carrying any explosives. It was carrying fuel which exploded when the truck slammed into a bus," Beck said. He confirmed that 10 civilians were killed and 15 injured.

Hospital officials said 20 people were injured in the incident that took place in al-Bayaa (search), a poor area in southwest Baghdad. The deputy interior minister, Ahmed Kadhim Ibrahim (search), said the all of the dead were Iraqis, and that the truck driver intended to strike a nearby police station.

The charred, crumpled bus lay in the intersection after the blast. Body parts were scattered in the area. A pink plastic sandal was left in the street. Two cars nearby were destroyed.

U.S. soldiers arrived and took photographs of the shattered remains of the truck.

"I was leaving home when I heard an explosion and saw cars burning at al-Bayaa intersection," said Ahmed Ayyoub, a 23-year bus driver.

"I ran to the place to see if there were people injured. There were lots of human remains on the sidewalks and we started collecting them," he said. The rescue effort was more difficult because it was still dark at the time of the blast, he said.

The explosion followed riots earlier this week in Baghdad by Saddam loyalists, who also ambushed a U.S. patrol in Samarra (search), stormed the office of a U.S.-backed mayor in Fallujah and battled American troops in Ramadi.

The 4th Infantry Division (search) and Iraqi forces started a new series of raids, dubbed Operation Ivy Blizzard, on Wednesday in Samarra.

A written statement from the division said the sweep was requested by local leaders and that it would "target, isolate and eliminate former regime elements and other anti-coalition cells."

Although Wednesday's explosion apparently was not caused by a terrorist, assailants have attacked the al-Bayaa station several times. Four days ago, police said, attackers fired rocket-propelled grenades at the station. U.S. soldiers left the station after that attack at the request of Iraqi police who believed the American presence was provoking attacks.

Medhat Ghanem, 32, said he was on the sidewalk waiting for a bus when he saw a yellow truck speed down the main road and explode.

"After the explosion, I fell to the ground and was unconscious for a bit. Then I found that my leg was broken," Ghanem said in a hospital where his leg was put in a cast.

Meanwhile, at least four people were injured at a pro-Saddam demonstration in the northern city of Mosul on Wednesday, witnesses said. They said passengers in a car opened fire on the protesters.

As soldiers fought off angry protesters and guerrilla attacks Monday night and Tuesday, the 4th Infantry Division said it had snared a leader of the insurgency and 78 other people in a raid north of Baghdad, not far from where Saddam was found three days earlier.

A roadside bomb wounded three American soldiers in Saddam's hometown of Tikrit, and a pro-Saddam demonstration Tuesday in Mosul ended in violence, with a policeman killed and a second injured.

President Bush said Saddam deserved the "ultimate penalty" but it would be up to the people of Iraq to decide whether he should be executed. In a television interview, the president also said Iraqis are "capable of conducting the trial themselves."

The United Nations, the Vatican and many countries worldwide -- especially in Europe -- oppose putting Saddam on trial before any court that could sentence him to death.

The chairman of the Joint Chiefs of Staff, Gen. Richard Myers, said Tuesday in Baghdad that military planners were preparing for American troops to stay in Iraq for up to two more years despite capturing the former Iraqi leader.

The 4th Infantry Division raid in the village of Abu Safa, near Samarra, about 60 miles north of Baghdad, began late Monday after insurgents in Samarra ambushed U.S. forces. The U.S. military said its troops killed 11 of the attackers, who released a flock of pigeons to signal one another that the American patrol was in range. No Americans were hurt.

By early Tuesday, U.S. troops arrested Qais Hattam (search), the No. 5 fugitive on the 4th Infantry's list of "high value targets," said Capt. Gaven Gregory. The guerrilla leader was described as a major financier of insurgents who have been fighting the U.S.-led coalition for months.

Hattam is not on the U.S. list of the 55 most wanted Iraqis. Thirteen fugitives from that list remain at large.

The Associated Press contributed to this report.