FOND DU LAC, Wis. (AP) -

Mercury Marine has begun a $20 million expansion at its Fond du Lac headquarters.

The construction plans were made after the company decided three years ago to move its Stillwater, Okla., operations to Fond du Lac.

Company spokesman Steve Fleming says the expansion will help Mercury stay competitive in the marine engine industry.

The Reporter of Fond du Lac reports that the areas being expanded include product development and manufacturing.

The company says about 90 percent of the construction work will be performed by Wisconsin companies.

Mercury Marine has more than 5,000 employees, including about 2,550 in Fond du Lac.