CANADA (From news reports) -- Four contractors at West Fraser's Cariboo Pulp and Paper mill in Quesnel were sent to G.R. Baker Hospital after a brief exposure to a by-product of the manufacturing process.

The black liquor vapour mist exposure happened at approximately 8 a.m. Thursday, May 19, during routine operations.

"The four individuals reported to first aid after experiencing minor respiratory and eye irritation," confirmed a West Fraser spokesperson.

"As a precaution, the individuals were transported by ambulance to local medical aid for observation and further assessment."

BC Emergency Health Services, RCMP and the Quesnel Volunteer Fire Department responded.

Upon arrival, fire chief Ron Richert said the incident was under control.

"Protection systems worked as designed and emergency procedures were immediately activated, including restricting access to the area," the West Fraser spokesperson added, thanking emergency responders.

"Public and employee safety are West Fraser's top priorities. Our operations have an excellent safety record as a result of our commitment to prevention and safe practices for those working in and around our site."

The cause of the incident is under investigation.