Bird flu has been detected in rats for the first time, the U.S. Department of Agriculture's Animal and Plant Health Inspection Service confirmed Wednesday. Four black rats were confirmed to have H5N1 avian flu in late January in Riverside County,

An Agriculture Department spokesperson told NBC News that officials are "working to swiftly rectify the situation."

The U.S. Department of Agriculture is trying to reverse the firing of some employees who were involved in responding to the nation’s growing bird flu outbreak, officials said this week.