AP

The Department of Agriculture has quarantined two farms in the wake of the latest mad cow disease investigation.

USDA authorities want to make sure the farms are not connected to the source of a case of BSE, or "mad cow," that can be fatal in humans.

An infected cow was discovered at a California rendering plant last month. The was euthanized after it "developed lameness and became recumbent," according to the USDA. Health officials say the cow was never intended for the meat market, and developed an atypical mutation of BSE. There is no suspected risk to the U.S. food supply.

USDA agents are working to see if any other at-risk cows are at a second farm associated with the Tulare County dairy farm, where the infected cow came from.

Offspring of the diseased cow were not found to have the disease.

This is the fourth case of case of BSE discovered in the U.S. since 2003.