10/27/2014 08:01 EDT | Updated 12/27/2014 05:59 EST

Sarnia explosion caused by dust collector outside building

An explosion that killed an employee and injured four others at the Veolia ES Canada plant in Sarnia, Ont., this weekend started in a dust collector outside the building, the Ontario Ministry of Labour said.

The explosion ripped through the Veolia ES Canada industrial cleaning and maintenance services facility Saturday afternoon, sending five employees to hospital with burn injuries.

Ministry spokesman Bruce Skeaff said the explosion caused significant structural damage.

"A City of Sarnia engineer had declared the building unsafe to enter," said Skeaff. "We issued a 'Do not disturb the scene' order to the company."

Two of the five injured employees were airlifted to hospitals outside Sarnia, one to Hamilton and another to London, Ont., for treatment.  The other three were transported to London by ambulance.

The employee who was airlifted to London, Ont. died as a result of his injuries early Monday, the Sarnia Police Service said in a news release. His name has not be released.

Veolia said it's co-operating fully with the Ministry of Labour and other authorities as they investigate the cause of the explosion

No chemicals were released in the blast.

The Ontario Fire Marshal continues to investigate at the industrial facility.