The driver of a van filled with refugees from Africa lost control and crashed on a southern Arizona highway Wednesday, killing five people and injuring 12 others, authorities said.

The vehicle rolled over a guard rail, down an embankment and landed on its wheels in the oncoming lane of Interstate 10 about 50 miles east of Tucson.

The director of a relief agency in Tucson said the van passengers were from the small eastern African nation of Burundi who had fled to a Tanzanian refugee camp before having relocated to Tucson.

The group was seeking work at Eurofresh Inc., a hydroponics vegetable grower in Willcox, Ariz., said Ken Briggs, executive director of the International Rescue Committee's Tucson office.

Jean Spinelli, a spokeswoman at University Medical Center, the only trauma center in southern Arizona, said six of the 11 survivors brought in from the crash were listed in critical condition and the other five in serious condition.

Tucson Medical Center spokesman Mike Letson said one person had been airlifted to the center. No condition was available.

The cause of the crash was under investigation.