FOLEY, Minn. (AP) - Federal investigators have searched a vegetable farm in the central Minnesota town of Foley but details on why remain sketchy.

A helicopter and at least a dozen unmarked SUVs and cars reportedly surrounded the house and another dozen surrounded a warehouse Thursday on the Svihel Vegetable Farm, owned by John and Julie Svihel.

John Svihel says he was surprised and that all of his migrant workers were there legally. He said none were taken away. However, he said investigators did seize computers and boxes of files.

The operation was led by Diplomatic Security, a law enforcement arm of the State Department. Besides protecting diplomats, it also investigates passport and visa fraud.

DS officials and the Svihels did not immediately return calls from The Associated Press Friday.