WHITEHOUSE STATION, N.J. (AP) — Merck & Co. said Monday it received a letter from federal prosecutors notifying the company it is "a target" of a grand jury investigation involving the painkiller Vioxx, which Merck pulled from the market in 2004. Merck has previously disclosed the investigation, which the company said has been ongoing since 2004. Monday's update said the company received a letter from the U.S. Attorney's Office in Massachusetts stating the company was a target. Christina DiIorio-Sterling, a spokeswoman for the U.S. attorney's office in Boston, declined to comment Monday. Merck said the investigation "relates to activities in connection with Vioxx." The company said it "has responded and is continuing to respond to requests from the U.S. Attorney's Office for documents and information in connection with the ongoing investigation." Merck pulled the painkiller pill off the market in September 2004 after its own research showed it doubled the risk of heart attack and stroke. The company said in November 2007 that it agreed to a $4.85 billion settlement designed to end the bulk of personal injury lawsuits stemming from Vioxx. Some of the lawsuits have claimed Merck knew of the cardiovascular risks from Vioxx since 1996, but used various strategies to conceal the risks and overstated the drug's safety and effectiveness in consumer ads. The company said in a regulatory filing last month that it had so far paid out $750 million from the settlement fund, with additional payments forthcoming.