A Christmas Eve explosion at the Co-op refinery in Regina is the latest incident to put a spotlight on safety at the complex.

The plant, which has gone through several upgrades and expansions in its 80-year history, has recorded five significant incidents in just two years.

The most serious was a 2011 blast that injured 36 people.

"This is an anomaly and not the norm," Randy Ryba, Regina's Fire Marshal, told CBC News, referring to the recent rash of incidents.

Ryba noted each one was different in nature, location, cause and the mechanisms that failed.

refinery after

The refinery after the Christmas Eve explosion.

The current investigation, into the Christmas Eve explosion, is being conducted by the fire marshal's office with assistance from the province's Technical Safety Authority.

Chief Inspector at the TSA, Chris Selinger, said he understands if some people have questions about safety at the refinery, but said they should be reassured.

"I understand right now that confidence has been weakened and eroded," Selinger said. "But there are things in place and all the different regulators are working to ensure it doesn't happen again."

In fact, Selinger said the refinery generally exceeds safety standards.

Still, the results of the current investigation will determine if more needs to be done to ensure safety.

Regina's mayor, Michael Fougere, said he is confident the plant will address any issues identified by investigators.

He too understands if people look at the frequency of incidents with concern.

"The more that happens the more concerned you become," Fougere said. "I'm not saying I'm not concerned. I'm saying that I'm very hopeful and confident that CCRL will find the source of the problem, fix it, and make sure it doesn't happen again."

Investigators say it will likely take a year to conclude their probe into the Christmas Eve explosion.

With files from CBC's Dani Mario