An American diasaster assistance official was shot and wounded on Tuesday while riding in a four-vehicle convoy in the lawless Darfur region of western Sudan, the State Department (search) said.

The woman suffered facial wounds and is being treated at a facility in Sudan. She will be evacuated to another country for additional treatment, State Department spokesman Adam Ereli (search) said.

Signs on the vehicle clearly showed it was being used for humanitarian purposes. The road had been considered safe for travel by the United Nations security office in Darfur.

Darfur has been plagued for more than two years by an ethnic conflict that has claimed the lives of tens of thousands and uprooted more than 2 million people.

The woman, whose name was being withheld, was one of 20 Sudan-based members of a disaster assistance team operated by the U.S. Agency for International Development (search).

"I think it's too early to say whether the person was targeted because she was a U.S. official," Ereli said.

He said the United States has asked for an immediate investigation by the Sudanese government and by African Union peacekeepers.