General Motors Co. will lay off 814 workers as it begins retooling its Detroit-Hamtramck Assembly plant for electric vehicle production in February, the automaker said in a filing with the state of Michigan.

The plant's 753 UAW-represented hourly workers will be offered transfers, likely to locations in Michigan and Ohio, GM said in a statement.

As part of a $3 billion investment, GM plans to start building an electric pickup and van at Detroit-Hamtramck. They would be followed by electric versions of the GMC Sierra and Cadillac Escalade, according to LMC Automotive, a closely watched provider of industry sales and production forecasts.

The union's contract with GM says employment at the plant eventually would triple to 2,225 workers at full production. Some workers displaced by the retooling may be able to transfer back as jobs open, but "hourly employee recall rights will be determined by the provisions of their collective bargaining agreement," GM spokesman Dan Flores said.

Automotive News reported last month that a lengthy layoff starting in early 2020 would be needed to make the conversion from gasoline-powered sedans to battery-electric trucks. The plant will stop making the Cadillac CT6 in January and the Chevrolet Impala in February.

GM gave formal notice of the layoffs in a state-mandated WARN notice filing Tuesday. Layoffs will begin Feb. 28 for most of the 800 hourly, 50 subsystem and 60 salaried workers affected. Fewer than 40 hourly workers will stay at the plant until March or April.

GM said it would invest $3 billion in the plant as part of GM's four-year labor contract with the UAW, ratified in October.

It did not say when production would resume, but CEO Mary Barra last month said she expects to have an electric truck in the market by fall 2021. LMC expects the retooling process to take about 18 months and that the plant's annual production capacity will decrease to about 100,000 vehicles, from 160,000 today.

Detroit-Hamtramck is the only one of four U.S. plants targeted for closure by GM's sweeping restructuring effort detailed a year ago that was saved under the new contract.