Investigators will start looking into the cause of an explosion at the Federated Co-op refinery in Regina on Friday.

A fuel processing tank exploded at about 3:30 p.m. CST on Christmas Eve and then a fire broke out. 

The explosion was felt throughout the city. Nobody at the refinery was hurt, but the large bang was felt as far as White City.

Ely Bersales, who was working at a store on Park Street when the explosion happened, said the blast shook the store and knocked items off of shelves.

"When we hear that there is a big explosion in the refinery, what I'm thinking about, and everybody is thinking about, is there anybody hurt?" Bersales said. "What happened? Because it was so strong, it's like the impact, and everything, because all of Regina could hear it."

Other people in the area said the explosion sounded like a car crash.

Angie Mamais, who owns a business near the refinery, said she's concerned about safety. 

"I just want everyone's safety. The workers there, they are our customers, we appreciate their business," Mamais said. "It is a little scary."

The scene remained secure Thursday and engineers have conducted a safety audit. The Regina fire department will begin its investigation tomorrow.

This is the fourth fire in about two years at the refinery.