Armstrong Tire said it may close its Hanford plant.

The New Haven, Conn.-based company set April 1 as closure date for the California plant. The Hanford factory produces replacement radial tires for passenger cars and light trucks and employs about 600 people. The company said it decided to exercise its right to cease operations at Hanford after a cost-reduction agreement with a union local failed to gain the approval of other locals covered by the same collective bargaining agreement.