Gov. Chris Christie says his office has received a subpoena from federal authorities investigating whether any laws were broken when lanes near a New Jersey bridge were apparently closed for political retribution.

Christie said Monday on a radio show that his office is cooperating with the U.S. Attorney's Office subpoena.

The Republican also says that he may have heard about traffic tie-ups in Fort Lee when they were going on last September, but that it didn't register with him as a major issue if he did.

He says a news report several days after the lanes were reopened got his attention and he asked staffers to look into it. The report indicated that the head of the Port Authority of New York and New Jersey did not authorize the closings.