March 14 (Reuters) - The U.S. Food and Drug Administration is studying unconfirmed reports that a widely used class of diabetes drugs, which includes Merck & Co's Januvia, may cause inflammation of the pancreas and pre-cancerous changes to the pancreas. The agency, in a notice on its website on Thursday, said it is the first time it has communicated potential pre-cancerous links to the medicines, known as incretin mimetics. The oral treatments also include Bristol-Myers Squibb Co's Onglyza. Patients should continue taking their medicines as directed until speaking with health care professionals, the agency said. The FDA said it is investigating findings from academic researchers that highlighted the potential risk. "These findings were based on examination of a small number of pancreatic tissue specimens taken from patients after they died from unspecified causes," the agency said. The FDA has asked the researchers to explain how they collected and studied the specimens and to provide tissue samples so the agency can further assess any possible risks. In the meantime, the FDA said it has not reached any new conclusions about safety risks of the class of drugs. The agency noted it has previously warned the public about acute pancreatitis, including fatal and nonfatal cases, seen with the medicines. Package insert labels for the class of drugs already warn about risk of the potentially dangerous inflammation. Merck's Januvia and its related drug called Janumet, had combined sales last year of almost $6 billion, making them by far the company's biggest product franchise. Onglyza and a related drug called Kombiglyze had sales last year of $709 million. Shares of Merck were down 1.3 percent, while Bristol-Myers slipped 0.5 percent, in morning trading on the New York Stock Exchange.