Provincial police say a man is now in stable condition after a shop fire near Arthur.
Crews were called to a propane reclaimation facility on Line 6 around 4 p.m.
Video shows flames shooting up from the ground, and what sound like explosions can be heard in the background.
Fire officials said there were multiple propane tanks on fire and they believe between 20 to 30 exploded.
Officials had closed Line 6 between Wellington Road 16 and Sideroad 13 in Damascus while crews battled the blaze on Tuesday afternoon.
Provincial police said in a tweet that several homes in the area had been evacuated. Around 5:50 p.m., police said that evacuees would be able to return to their homes.
A spokesperson for Ornge says that the injured person, in his 50s, was taken to Hamilton General Hospital in critical condition.
Police say he received third degree burns to over 30 per cent of his body, but is now in stable condition.
"When he was working in the shop, apparently a cylinder fell over and was leaking propane, and then there was a spark and that's what caused the explosion," said David Guilbault, Wellington North Fire Chief.
Damage is estimated at $300,000.
The Ontario Fire Marshall has been contacted.
