ANCHORAGE — Alaska’s attorney general is again seeking an explanation from the U.S. Department of Justice on why it did not file child exploitation charges against a businessman who testified in the corruption trial of the late U.S. Sen. Ted Stevens.

Alaska Attorney General Craig Richards on Friday announced he has formally asked U.S. Attorney General Loretta Lynch for permission to prosecute Bill Allen or explain why the state’s request has been denied. He said there’s a lingering sense that justice has not been served.

“The ball got dropped,” he said at a press conference.

Allen was the head of an oil field service company at the center of a federal investigation of corruption in Alaska politics. He testified in three trials, including the trial against Stevens, the longest-serving Republican senator in history, who was charged with failing to report gifts.

The jury verdict against Stevens was eventually set aside and the indictment dismissed amid charges of prosecutorial conduct. By then, Stevens had lost his re-election bid. Stevens died in a plane crash in 2010.

Allen pleaded guilty to bribery and other charges.

Richards said federal and Alaska investigators found evidence that Allen violated the federal Mann Act by transporting an underage prostitute across state lines, from Seattle to Anchorage, for sexual purposes.

The state twice asked that the Justice Department to allow state prosecutors to prosecute Allen under the federal law and twice was denied, without reasons, Richards said, such as a plea deal for Allen’s testimony in the corruption trials.

A change in the Mann Act allows Alaska to ask again. A revision pushed by U.S. Sen. Dan Sullivan, R-Alaska, and a former state attorney general, said the U.S. attorney general must grant a request by a state attorney general to “cross prosecute” under federal law unless granting that request would “undermine the administration of justice.” Sullivan appeared at the state Department of Law news conference Friday.

If the request is denied, the revised law requires a detailed reason within 60 days.

The young woman, now an adult, sued Allen in 2014 and accused him of sexual assault and emotional distress. The Alaska Dispatch News reported last year that Allen in response to the lawsuit acknowledged a paid relationship with a teenage girl but that she told him she was 19, not 15. His attorney in the case, Paul Stockler, was not immediately available Friday afternoon.