Integrated Health Services Inc. said yesterday that the Department of Justice is investigating activities of a medical testing subsidiary in Florida.

The Owings Mills, Md.-based company said in a statement that it was "cooperating fully" with the investigation, which it said involves a subsidiary that provides tests of a patient's swallowing function.

Company officials were not immediately available for further details or comment. Trading of company shares was briefly halted on the New York Stock Exchange after the statement's release.

"Annualized revenue for the company's modified barium studies division in Florida is approximately $800,000 and total annualized revenue for the company's modified barium swallow studies division throughout the country is approximately $2 million," the firm said.

Integrated Health Services reported a net loss from continuing operations of $4.6 million in the second quarter on net revenue of $625 million--a decline of 16 percent from the second quarter of 1998.

The company operates a variety of medical services, including respiratory services, long-term care and contract rehabilitation services. It operates over 1,600 post-acute service locations in 48 states.

After trading was resumed, shares closed yesterday at $2.81 1/4, down 25 cents.