* UAW official says plant to close by end July

* Says production moving to Mexico

* Detroit plant has 734 active UAW employees (Adds details of plant closure from UAW official, background, comment from American Axle, stock action)

DETROIT, April 28 (Reuters) - U.S. auto supplier American Axle & Manufacturing Holdings Inc (AXL.N: Quote, Profile, Research) is set to close the largest axle plant in its Detroit-area manufacturing complex and move production to Mexico, a United Auto Workers union official said on Tuesday.

"People are very upset about losing their jobs," said UAW Local 235 President Bill Alford. "They're very upset that a company with the word 'American' in its name is moving jobs to Mexico."

Alford said American Axle had informed the UAW the plant would close by mid-July and production would move to Guanajuato, Mexico, by the end of July.

There are currently 734 active UAW-represented workers employed at the plant, Alford said.

"All of those jobs are going to Mexico," he said.

The plant produces axles for heavy-duty pickup trucks, he added.