A U.S. Senate committee has launched an investigation into reports that doctors with financial ties to the medical device company Medtronic were aware of serious complications with a lucrative spine surgery product yet failed to reveal those problems in medical journal articles. Citing reports in the Journal Sentinel, two leaders of the Senate Finance Committee sent a letter to Medtronic on Tuesday demanding an extensive trail of documents, including financial records and communications between the company and doctors who have received millions in royalties and other payments. Medtronic was warned not to destroy any of the documents, data or other information in the letter signed by committee chairman Max Baucus (D-Mont.) and senior member Chuck Grassley (R-Iowa). The growing controversy involves Medtronic's spine surgery product Infuse, which was approved by the Food and Drug Administration in 2002.