Marc Couture, 42, sustained burns to 90 per cent of his body and was kept in a medically-induced coma since Thursday.
According to authorities, his family made the decision to take him off life-support after consulting with doctors.
Couture had three children aged 13, 16 and 18.
José Duguay, a friend of the victim, told CBC's French service, Radio-Canada, that Couture had been working at Neptune Technologies for about two weeks before the explosion.
Couture worked as a mechanic for the plant and was responsible for repairing leaks and breaks in the pipe system.
Duguay, who is a former employee at the plant, said Neptune was a great work environment but told Radio-Canada he will push to find a reason for the explosion.
He said he thought the construction at the plant may have led to a lack of work safety at the plant, but insisted to say those were his doubts.
To date, the explosion caused three deaths and injured 18 people. According to authorities, many of the people injured suffer from burns of varying severity and many showed symptoms of shock.
Massive fire followed explosion
The blast happened at about 1:30 p.m. ET on Pépin Street.
The company makes health products from krill oil, which contains omega-3 fatty acids.
The explosion sparked a massive fire that took emergency crews hours to get under control and triggered fears of toxic exposure due to the acetone at the site.
Environment Quebec later said the fumes from the fire were not toxic and local residents should not be worried.
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