Eight people were sent to hospital with burns, while two others were treated at the facility owned by Consumer's Cooperative Refineries Ltd.
The company did not say what condition they are in.
All 10 were contractors working on a $1.9-billion expansion of the refinery.
In total, there were 450 day staff and nearly 1,000 contractors on site, all of whom were evacuated from the facility.
The Co-op refinery in Regina was evacuated because of the fire.Jordan Jackle/CBC
Witnesses told the CBC that the fire began after a large explosion at the diesel processing area of the facility at around 2 p.m. CST.
One worker told CBC News that after the explosion, he saw a giant fireball that was so hot it melted steel.
Emergency crews battled the fire as flames and black smoke shot into the sky.
There were concerns that the fire could spread and ignite gas and diesel tankers on the other side of the facility.
By shortly before 3 p.m., the fire was under control.
Refinery officials say there is no danger to the public.
They say they have found the ignition point of the fire, and suspect the cause was a pipe leaking a mixture of hydrogen gas and diesel fuel that found a spark.
It is the worst fire at the refinery in 20 years.