As contradictory and confusing bird flu test results come back from various county and state agencies, the state's agriculture department has instructed raw milk producer Raw Farm to withhold sales.

California health officials are warning not to drink another lot of raw milk from Fresno-based Raw Farm after it tested positive for bird flu virus. More testing of Raw Farm products is underway, the state said.

The detection of bird flu virus this week in a batch of unpasteurized milk sold in California underscores what health experts say are the known and potential risks of the products.