Armed with grinding wheels and box cutters, fire crews painstakingly worked to cut away at quickly hardening tar that severely burned and enveloped a man after spilling from a five-tonne truck in Toronto on Monday morning.

As the clock ticked, the molten tar cooled, solidifying with each passing second. But underneath the surface, the tar was still a scalding 204 C — hot enough to severely burn not only on the man, but also the crews working to free him.

"We train for everything … but this this is something we've not seen to this extent before," Toronto Fire Services platoon chief Dave Denysek told CBC News.

A total of 18 firefighters and four trucks were called to Logan and Danforth Avenues, in Toronto's east end, just before 8 a.m. after a road-repair truck carrying the hot liquid was forced to come to a hard stop.

Firefighters and paramedics free injured worker from hot tar truck 0:37 The tar overflowed, covering a 46-year-old worker, who had been at the back of the truck. Police originally said the man was in his 30s.

"It was quite a large spill; knocked him down and actually flowed all over him," Denysek said.

The responders' first task: surveying the scene for safety.

"It's quite a big tank of molten tar … that's a significant hazard," Denysek said. "Right away, that's our assessment: 'Is this going to let go and trap us and cause further problems?'"

“We train for everything… but this this is something we’ve not seen to this extent before,” Toronto Fire Services platoon chief Dave Denysek told CBC News. (CBC)

Once the scene was secured, firefighters split into three crews: one on the inside of the truck, another on the outside and one on top. They then set about cutting out a portion of the side of the truck to get at the inside.

As crews worked to free the man, they soon realized the more tar they removed, the deeper he would sink into the still-hot, liquefied layers below.

A total of 18 firefighters and four trucks were called to the scene at Logan and Danforth Avenues, in Toronto's east end, just before 8 a.m. (CBC)

"Every time they would cut, he would drop a couple inches back into the stuff, causing further burns," Denysek said.

So the quick-thinking crews used a heavy-duty truck strap to fashion a hammock-like system to keep the man suspended as they worked to free him, using a combination of power tools, skill saws and regular box-cutter-style knives to cut him out — an eighth of an inch at a time.

In all, Denysek said the man was trapped for about an hour, suffering severe burns in the process.

"He was definitely in significant pain," he said.

Police said the man was wearing a protective suit but remains in hospital with critical injuries.

The Ontario Ministry of Labour has been notified.