Medtronic says it has received a civil investigative demand from the Massachusetts prosecutors seeking documents related to the company's CoreValve division, which makes heart valves.
The authorities are looking for information on Fridley-based Medtronic's relationship with heart specialists at a clinic in Burlington, Mass.
The clinic is affiliated with the Tufts University School of Medicine.
A spokeswoman for the U.S. Attorney's office declined to comment on the investigation.
Medtronic has already received several subpoenas from the Massachusetts office seeking information about its products, marketing, and payments to physicians.
Medtronic spokesman Chuck Grothaus says the company was working with the clinic to test a new minimally invasive heart valve procedure.
"Our process to select potential clinical research sites for the US CoreValve trans-catheter valve clinical study was designed to be fair, objective and independent of commercial interests," he said.
Grothaus says the company is cooperating fully with the government.