A swarm of bees that attacked a work crew earlier this month may be of the Africanized variety, which would mark the furthest north the so-called "killer" bees have traveled in the United States, scientists said.

DNA tests show the bees have Africanized traits, said Russell Wright, head of the Department of Entomology and Plant Pathology at Oklahoma State University (search).

"They certainly are more Africanized than European," he said.

Wright said the bees have been sent to a U.S. Department of Agriculture (search) Laboratory in Arizona for final confirmation. Those results are expected to take three to four weeks.

Wright said it will be the furthest north the so-called "killer bees (search)" have traveled in the United States.

The bees were discovered when a work crew cut through the limb of a storm-damaged tree last month in the southwest Oklahoma community of Tipton.

"We all ran different directions to the vehicles, and they followed us. There were just so many of them," said Jeff Marshall, a city worker who was stung between 35 and 40 times.

Seven members of the work crew were treated at a hospital.

Similar to common honey bees but dangerously aggressive, Africanized honey bees have been detected in New Mexico, Texas, California, Nevada and Arizona. They were first found in Texas in 1990.

The bees' venom is no more toxic than the European honeybee, but they are more dangerous because they attack in larger numbers.

"When they sting, they give off an odor or a pheromone that attracts other bees," he said, "and they will follow you a long way."