SACRAMENTO, Calif.—Millions of swarming honey bees are on the loose after a truck carrying crates of the insects flipped over on a California highway.

The California Highway Patrol says 8-to-12 million bees escaped Sunday from the crates in which they were stored and swarmed over an area of Highway 99 and stung officers, firefighters and tow truck drivers trying to clear the accident.

CHP Officer Michael Bradley says a tractor trailer flipped over while entering the highway on its way to Yakima, Wash. The flatbed was carrying bee crates each filled with up to 30,000 bees.

Bradley says several beekeepers driving by the accident stopped to assist in the bee wrangling.

The bees had been used in the San Joaquin Valley to pollinate crops.