Read: Senators' Letter to Fridley-based Medtronic

Three U.S. senators sent a letter to Fridley-based this week, asking the company how it tracks its products' performance.

The letter, one of the five sent to med-tech firms, specifically mentions Medtronic's product Infuse, citing "allegations that researchers who received funds from Medtronic, sometimes millions of dollars, did not report negative findings from clinical trials."

The Dec. 13, 2011, letter is addressed to Medtronic Chairman and CEO Omar Ishrak, who .

Senators Charles Grassley (R-IA), Herb Kohl (D-WI) and Richard Blumenthal (D-CT) signed the letter. The same three are sponsors of new legislation to require manufacturers to monitor their devices in patients.

Medtronic told the Star Tribune"We have received the letter and are working to comply with their request."