BELLINGHAM, Wash. -- Nineteen people are being treated at St. Joseph Hospital in Bellingham after suffering carbon monoxide poisoning at a waterfront seafood processing plant, hospital and fire department officials said.

The patients are in the hospital's emergency room and will be there for three or four hours, said Noreen Fassler, a representative of the hospital. Four patients are being taken to Virginia Mason Medical Center in Seattle for treatment in hospital's hyperbaric chamber.

Bellingham Fire Department Chief Bill Boyd said the victims were overcome by fumes Tuesday morning at Homeport Seafoods, a seafood processor.

Boyd said the call for help came in at 8 a.m. When firefighters arrived, they found a number of people exhibiting symptoms of exposure to carbon monoxide, including shortness of breath, nausea, faintness and elevated heart rates.

The fire chief said that after giving patients oxygen at the scene, 16 people were transported to the hospital by Bellingham Fire Department aid units and Whatcom Medic One paramedic units. Others went to the hospital on their own.

Boyd said elevated levels of CO were found at the business. Fans were installed and the building has been aired out. The chief said several forklifts were operating inside the closed building Tuesday morning and the CO may have come from them. The official source of the fumes has not been determined.