Public health officials in Minnesota say they're responding aggressively to the potential swine flu threat.

But they say lab tests on 12 patients with flu-like symptoms have found no confirmed or probable cases in Minnesota so far. Samples from those 12 patients all tested negative for swine flu.

Since last Thursday, the Minnesota Department of Health has been asking hospitals and doctors to submit specimens if they have any patients with the kind of respiratory symptoms typical of influenza.

State Epidemiologist Ruth Lynfield says the state and local health departments have been preparing for major public health threats for years, and are ready to respond.

Testing will continue, and health officials expect to find some swine flu cases in Minnesota eventually.