Agriculture officials plan to quarantine fruits and vegetables in up to 80 square miles of San Jose after finding two Mediterranean fruit flies (search) — pests that don't pose a threat to humans but can ruin crops.

The California Department of Food and Agriculture declared an infestation in part of the city after the insects, commonly known as Med flies, were discovered last week in a lemon tree and an apple tree in a residential neighborhood.

"Travelers will often bring fruit back, unknowingly bringing back pests," said Mert Pllion, said Steve Lyle, a spokesman for the Department of Food and Agriculture.

"We've never had an uncontrolled infestation, but any infestation is a major event," Lyle said.

There are no commercial agricultural operations in the area where the two Med flies were found, he said.

The quarantine (search) was expected to begin in the next several days. Fruits, plants or vegetables would be prevented from leaving the quarantine area. State officials have not yet set the exact boundaries for the quarantine.

Processed fruit and vegetables would not be affected.

The department on Thursday released about 1.25 million sterile flies in a 10-square-mile area of San Jose. The sterile flies are meant to mate with Med flies to keep them from reproducing.

Med flies previously caused quarantines in the state, mostly in Southern California. During the 1980s and '90s, several countries banned products that were grown in quarantined areas.