Labour officials in Nova Scotia are investigating a pharmaceutical plant following the death of a lab worker this week.

The Labour Department confirms the 46-year-old quality-control technician died in hospital Wednesday, about 18 hours after he inhaled D-Malic acid at the facility in Windsor.

Three other workers at the Sepracor Canada Ltd. plant were also exposed to the compound.

The department has issued a stop-work order for the laboratory. The rest of the facility remains open.

"The lab has been closed to performing this procedure with this material until further notice," Labour Department spokeswoman Jacqueline May told CBC News Friday.

"The company has also been ordered to provide the department with their health and safety procedures, and the company is going to be carrying out an incident investigation of their own, to be completed by Oct. 24."

May said investigators are examining protective equipment in the area where the technician was exposed to the compound, which is used in the analysis of drug ingredients.

"It's something dangerous enough that it is normally used within a fume hood. But in this particular case, as part of a larger investigation, we are looking into whether or not a fume hood was operating properly at the time," she said.

'Unaware of any link'

The company is questioning the connection between the technician's death and his job.

"Sepracor has been informed that the employee had been home for several hours after leaving work in apparently good condition on Oct. 7," Sepracor said in a statement.

"Sepracor is unaware of any link between the employee's work duties and the condition he reported in hospital, and is co-operating with all concerned authorities, including the Department of Labour."

No other employees at the plant have reported similar medical conditions, the company added.

A Sepracor spokeswoman declined to answer questions from CBC News.

The Windsor plant employs 70 people.