Federal agents Thursday seized quantities of a contaminated blood thinner made in China from a small manufacturer in Cincinnati, officials said.

The blood thinner heparin, given to patients undergoing heart surgery and kidney dialysis, was the focus of a major recall earlier this year after crude drug material from China was found to be contaminated. Hundreds of frail patients suffered severe allergic reactions. The government received reports of nearly 250 deaths.

The FDA had inspected the Cincinnati company, Celsus Laboratories, Inc., in April and at the time found contaminated heparin in two different kinds of products, officials said. A little over 2 pounds of the blood thinner was intended for use directly with patients, and another 31 pounds was to be utilized in diagnostic test kits and medical devices.

The FDA seized the heparin after informing the company that its efforts to notify customers of the contamination problem were unsatisfactory, the agency said in a statement. Drug seizures are a rare penalty for the FDA, since regulators prefer to negotiate with manufacturers to resolve disputes.

A representative who answered the phone at Celsus said the company would have no comment.