Clashes between the Afghan army and a renegade warlord killed two Afghans, and an Arab possibly linked to al-Qaida was arrested, an army commander said Friday. A U.S. jet dropped a bomb to stop to the fighting.

Elsewhere, U.S. officials said a rocket exploded about 2 miles from a U.S. special forces' safe house Friday in Paktia province, a main area of activity in the search for Taliban and al-Qaida holdouts in southeastern Afghanistan.

Fighters from the Afghan army and Maulvi Noor Mohammed, a local warlord, skirmished on Thursday in Nangarhar province in eastern Afghanistan, said the main Afghan army commander in the province, Hazrat Ali.

Ali said two people were killed, including the warlord's brother, and six people wounded in the clashes 40 miles west of Jalalabad. A U.S. military spokeswoman, Col. Roger King, said U.S. special forces dropped a 500-pound bomb in an uninhabited area to stop the fighting.

Ali said there was "al-Qaida activity" in the area and that one Arab was arrested during the fighting, though it was unclear what the Arab's connection was to the clashes.

Ali blamed Mohammed for starting the fighting. But sources in Jalalabad, the capital of the Nangarhar province, said the clash followed an attempt by Ali to disarm local residents in the area. They resisted and a gunbattle broke out.

Coalition forces, meanwhile, detained a man who they thought was a biological weapons smuggler, but lab tests show the materials he had in his possession contained neither chemical nor biological agents, King said.

Forces detained the man July 10 in the village of Hesarak after intelligence sources said he had suspected ties to al-Qaida and the Taliban, King said. Two others were also detained.

Special forces took "block shaped and paste-like materials from the house that the smuggler was taken from," he said. Tests in the Afghan capital Kabul detected the possible presence of the biological agent Ricin.

But further tests in the United States determined the materials did not contain any biological or chemical agents. When asked if the materials found could have been drugs or materials to process drugs, King said, "possibly."

Equipped with gas masks and gloves, U.S. forces swooped into the village for a second time on Tuesday and found more of the materials plus "documents deemed to have intelligence value," King said.

Some people in the village, which is 60 miles south of Kabul, complained the three men detained July 10 were not guilty of anything and had no links to al-Qaida or the Taliban.

Meanwhile, Afghan President Hamid Karzai filled one of the Cabinet posts left empty when top official Abdul Qadir was slain earlier this month. Abdullah Ali, deputy of Kabul's city construction ministry, was picked to take over as minister of public works, one of three positions Qadir held.

Qadir's other posts -- vice president and governor of the eastern Nangarhar province -- have not yet been filled, said government spokesman Said Fazel Akbar.

Qadir was gunned down July 6 outside his office by two men who fled in a white vehicle. He was the second government minister killed in the capital of Kabul in six months.