Nova Scotia labour officials have determined that a technician at a pharmaceutical plant was exposed to a toxic chemical while working in a lab without proper ventilation before he died.

The mysterious death of Roland Daigle, 46, seven months ago remains under investigation.

Daigle, a quality-control technician, died in hospital on Oct. 8, about 18 hours after working with trimethylsilyldiazomomethane at the Sepracor Canada Ltd. laboratory in Windsor.

The chemical is toxic if inhaled.

Jim LeBlanc, director of the province's occupational health and safety division, confirmed that the lab's protective fume hoods were turned off so that work could be done on the roof.

Officials are trying to answer why Daigle was working with a life-threatening chemical without adequate ventilation.

"The employer had provided information to their staff that the fume hoods would be turned down to accommodate the work," LeBlanc said.

"We also understand that he was given direction to conduct the assessment of … the product, so we need to understand what led him to do that work."

Sepracor questions the link between Daigle's death and his work duties.

In a statement last October, the company said Daigle appeared to be in good condition when he left work, and it was unaware of any connection between his job and his condition in hospital.

Occupational health and safety investigators have yet to hear from the medical examiner's office, which has ordered toxicology tests.

It could be the summer before an official cause of death is released.