The loud explosion and fire that rocked a Regina refinery on Tuesday afternoon was caused by liquefied petroleum gas, the city's deputy fire chief said said on Twitter.
The noise from the blast, which went off at about 3:30 p.m. CST, could be heard around the city.
By 5 p.m., the flames at the Co-op Refinery were 95 per cent contained, fire officials said.
People in the area who witnessed the incident said they saw fire and smoke coming out of the complex, which is on the city's northeast side.
Regina city councillor Wade Murray said he was on the Ring Road driving by the refinery when the explosion rocked his truck.
A source at the scene told CBC News the explosion and fire happened in the poly reactor, a section of the refinery where liquefied petroleum gas, or LPG, is made.
Fire officials said it appeared no one was injured.
Within an hour of the blast, there was still some smoke coming out of the refinery, but it appeared the fire was mostly out.
Fire trucks and ambulances were seen leaving the area a few minutes later.
There's no word yet on what might have sparked the gas.
There have been several explosions and fires at the refinery complex over the last 25 years, the most serious being one in October 2011, which injured 36 people.