WASHINGTON, Jan. 31 (Xinhuanet) -- At least 16 workers were injured Tuesday in an explosion at a chemical plant in the southeastern U.S. state of North Carolina, local media reported.

    One of the injured workers, who was in serious condition, was airlifted for treatment from the site of explosion at a Synthron Inc. plant in Morganton to Charlotte, in the south of the state.

    Another was airlifted for treatment in Winston-Salem, in the north-central of the state, and 14 others were being treated at Grace Hospital in Morganton.

    The blast set off an intense fire with thick black smoke, and police urged residents nearby to stay indoors while authorities were determining if it was harmful to breathe.

    Firefighters were on the site fighting to put out the fire, andit was not known immediately what had caused the explosion. Enditem