A group of Sudanese aid workers were released by rebels early Wednesday after four days of captivity, a U.N. official said.

Barry Came of the U.N. World Food Program (search) said the six aid workers — three from WFP and three from the Sudanese Red Crescent — were safe and well and being debriefed by a U.N. security team in Al-Fasher after being picked up by helicopter in Tabit, south of Al-Fasher, Wednesday morning.

Al-Fasher is the capital of North Darfur (search), one of the region's three states.

Officials had originally said eight workers were missing, but Came corrected that on Wednesday, saying two workers scheduled to have gone out with the team never made the trip because of illness.

The team had been assessing conditions and registering displaced people.

"They were picked up this morning after daybreak. They were being held by the SLA (rebel Sudan Liberation Army) and their release resulted from extensive negotiations with the local SLA commander." Came said. "I am told they are safe and healthy and happy to be home."

The Sudan Liberation Army had earlier denied it was holding the missing workers.

In June, 16 relief workers from international aid organizations were detained for several days in North Darfur, one of the region's three states, by the Sudan Liberation Army. The rebels said they had stopped the workers to ascertain their identities because they were in a military zone. The United Nations said then that the detention was "totally unacceptable" and contradicted rebel promises to facilitate relief work.

The Sudan Liberation Army is one of two African rebel factions that took up arms in February 2003 claiming discrimination by the Arab-dominated government in the capital Khartoum.

Human rights groups, the U.S. Congress and U.N. officials accuse the government of trying to crush the rebellion by backing Arab militiamen in a scorched earth campaign. Khartoum has repeatedly denied backing the militia, known as the Janjaweed, who are blamed for killing thousands, raping women and driving more than 1 million villagers from their homes.