Authorities say a bullet apparently was fired into an office of a Democratic congressman who has been an outspoken opponent of the state's immigration law.

The apparent bullet hole was found in a window Thursday in the Yuma office of Rep. Raul Grijalva (gree-HAHL'-vuh).

The discovery came on the same day that vocal immigration protests were held in Arizona. A judge a day earlier delayed most of the controversial new law from taking effect.

Yuma police are investigating to determine whether the bullet discovery is related to immigration.

Grijalva called for a national boycott of Arizona after the law was passed in April. He reversed course after the judge's ruling.