Old Saybrook – Four people were taken to the hospital for evaluation Thursday following exposure to smoke from a fire at a local factory that has raised concerns about exposure to toxic vapors, according to state environmental officials.

The Old Saybrook Fire Department initially was called out to extinguish a machine fire at Sound Manufacturing, a precision metal cutting operation at 51 Donnelly Road, which uses a laser in its processes, state Department of Energy and Environmental Protection spokesman Dennis Schain said.

After the fire was extinguished, the DEEP's Emergency Response Unit was called at about 6 p.m. because of concerns that focused on the fact that the laser's lens, which is coated with zinc selenide, can release toxic and flammable vapors when exposed to high heat, Schain said.

Employees who were exposed to the smoke appeared to have symptoms of respiratory irritation, Schain said. Four employees were decontaminated and taken to Middlesex Medical Center in Essex for evaluation.

At 9 p.m., DEEP officials remained on site with local fire and police as well as Guilford Fire Department and Naval Submarine Base Fire Department hazardous materials teams. They were expected to make a joint entry into the building to determine whether the lens is cracked and whether there is resulting contamination, Schain said.

Both police and fire departments declined comment.