(Nati Harnik/AP Photo)

It's taken more than a week, but the U.S. Department of Agriculture has finally found two offspring of the dead bovine with mad cow disease found in Central California on April 24. 

One of the cows born to the mad cow over the last two years was stillborn and the other was located at a dairy in another state, where it was euthanized and had its brain cells tested. 

The test results for mad cow disease, or BSE as it is also known, were negative, the USDA said.

Outside experts have told ABC News that because the original mad cow showed no signs of the disease before it was randomly identified during a test at a rendering plant in Central California, its offspring and "cohorts," cows born at the same place and within the same year, should also be found and tested.

The USDA has not found the original herd members, so they have not been tested. 

However, for reasons that were not immediately clear, a hold order was placed on all cattle at a second dairy associated with the dairy of the initial cow that tested positive for BSE.  Both dairies remain under quarantine. 

The mad cow found April 24 was the fourth case identified at U.S. farms, and no American has ever contracted mad cow disease from beef raised in the United States.