Commission investigates nuclear medicine division of Covidien. Source: Cedars-Sinai Health System

Federal regulators from the Nuclear Regulatory Commission (NRC) are inspecting Mallinckrodt, a business unit of Covidien that makes products used in nuclear medicine, after high levels of a nuclear isotope were extracted from its generators.

The NRC on Wednesday said it sent a letter and inspectors to Mallinckrodt, confirming its commitment to investigate a problem identified with isotopes extracted from generators used for diagnostic imaging by nuclear pharmacies and hospitals.

The company received information from customers last month that the liquid withdrawn from dozens of generators showed higher levels of the nuclear isotope than expected.

The company had sent the generators — containers of molybdenum-99 coated with a protective aluminum tubing — to more than 100 customers around the United States.

NRC spokeswoman Viktoria Mitlyng said it was not clear whether any patients had been injected with solution from the generators at issue, but even if that had occurred, it was not expected to pose a danger. She said the radiation level is still low so that even though it stays in the system longer, no adverse effects can be expected.

A special government inspection team this week began evaluating the cause of the problem, Mallinckrodt's response to it, the company's past actions and its follow-up on commitments to the government.

A Mallinckrodt spokeswoman said the Hazelwood, Mo.-based company is fully cooperating with the NRC and "has already taken actions it believes will help to mitigate this issue."

The government said its team will issue a report about 45 days after completing the inspection.