CHICAGO (Reuters) - The U.S. Department of Agriculture said on Monday it is collecting samples of ground beef in states with outbreaks of bird flu in dairy cows for testing but remains confident the meat supply is safe.

The USDA will analyze the ground beef to determine "whether any viral particles are present," according to a statement.

The U.S. Food and Drug Administration said on Friday that tests of milk showed pasteurization killed the bird flu virus, as Colorado became the ninth U.S. state to report an infected dairy herd.

There are no known cases of bird flu in beef cattle so far.

The USDA is collecting muscle samples at slaughter facilities of dairy cattle that have been condemned to determine the presence of viral particles. It will also use "a virus surrogate" in ground beef and cook it at different temperatures to determine how the virus is affected, the statement said.

(Reporting by Tom Polansek; editing by Jonathan Oatis)

By Tom Polansek