Christie fires top aide

TRENTON, N.J. (AP) — New Jersey Gov. Christie says he knew nothing of a plan by some of his closest aides to create traffic jams as political payback to a town mayor.

Christie spoke at a news conference Thursday. He says he had "no knowledge or involvement in this issue in its planning or execution." He adds that he was stunned by the "abject stupidity that was shown."

The governor also says he is responsible for their actions. He announced the firing of one close aide. Emails and texts show that she arranged lane closings to punish the mayor of Fort Lee, who didn't endorse Christie for re-election. The closings created gridlock for several days last fall.

The scandal threatens to upend Christie's second term and likely run for president in 2016.

Meanwhile, the  U.S. attorney in New Jersey says he is investigating the incident. A spokeswoman for U.S. Attorney Paul Fishman says in a statement that the Port Authority's inspector general referred the matter to Fishman's office.

Fishman says in a statement that his office is "reviewing the matter to determine whether a federal law was implicated."