Diamond Offshore Drilling Inc. said on Tuesday it was unable to comment on reports of a leak near its Ocean Saratoga rig in the Gulf of Mexico, as its shares tumbled nearly 6 percent.

The Alabama Press-Register, citing a federal document, and Business Insider both carried reports of the leak, which they said has been going on at least since April 30.

Gary Krenek, Diamond's chief financial officer, said while his company was required to report spills off the rig itself, and had not done so, the company was contractually unable to discuss anything further. He referred Reuters to New Orleans-based Taylor Energy Co. LLC, the Saratoga's operator.

Taylor was not immediately available for comment.

Shares of Diamond, which was downgraded along with its deepwater drilling rivals by Goldman Sachs earlier on Tuesday, were down 5.7 percent at $55.83 in afternoon trading on the New York Stock Exchange.