Firefighters have confirmed that an ammonia leak was responsible for the deaths of three people at an arena in Fernie, B.C., on Tuesday.

Mary Giuliano, the mayor of the small mountain community, told reporters at a news conference Wednesday that two of the dead were city employees, but they will not be identified at the request of their families.

"Fernie is a tight-knit community, and I know we will pull together to support each other as we have in the past," she said.

The third victim was a Calgary-based employee of CIMCO Refrigeration, according to Paul Jewer, executive vice-president of CIMCO's parent company, Toromont.

Jewer told CBC News that CIMCO has staff in Fernie to help however it can, and members of the management team are en route to the community to assist.

"In the meantime, we are focused on the well-being of all those affected. Our thoughts and prayers are with the families and the team," Jewer said.

Fernie resident Chris Inglis has set aside an area for mourners to remember three workers killed in the ammonia leak on Tuesday. (Chris Inglis)

Lifelong Fernie resident Chris Inglis has set up a memorial area outside the arena, where mourners can lay flowers and other tributes to those who died. He told CBC News he knew both local victims, and both were positive presences in the community.

"We're making the headlines for all the wrong reasons and I just can't really process it. The only thing you can hope [to do] is show love and support for families of the victims and their co-workers and their friends," Inglis said.

Late on Wednesday, city officials said crews had been able to enter the west side of the building, but the east remains too hazardous.

Evacuees are settling in for a second night away from homes and businesses in the care of emergency social services.

Ammonia used in refrigeration systems

According to fire Chief Ted Ruiter, the chemical responsible for the deaths is anhydrous ammonia, a noxious gas that can cause fluid to accumulate in the lungs if it's inhaled. Ammonia is commonly used in mechanical refrigeration systems, including those found in ice rinks.

Two city employees and an employee of CIMCO Refrigeration died inside the arena following the ammonia leak. (Google Street View)

Ruiter said that when first responders arrived outside the Fernie Memorial Arena on Tuesday afternoon, they found someone performing CPR on one victim, who died at the scene. The other two victims were found dead inside the arena.

B.C. Premier John Horgan and Labour Minister Harry Bains released a joint statement Wednesday morning, saying their thoughts were with the families of those who died.

"Neither workers nor their families should have to fear for their safety when they are on the job. Tragedies like this force us to underscore our commitment to ensure that B.C. families can rely on safe workplaces," the statement read.

Tragic news about the three lives lost in a Fernie workplace incident. Families and friends are grieving and our hearts are with them. —@jjhorgan

Irene Lanzinger, president of the B.C. Federation of Labour, said all workplaces need to ensure that chemicals like ammonia are being handled safely.

"Sadly, one of the things that happens is, after the fact, people look and say, are we doing everything we could?" she said. "Our goal is to have that increased level of attention before someone dies."

Emergency repairs to refrigeration system

The arena had been closed Tuesday morning to deal with emergency repairs to the rink's refrigeration system. What happened next is not yet clear.

CIMCO Refrigeration released a statement saying it was unable to provide any details about what went wrong.

"We are aware of the tragic event that happened yesterday in British Columbia," the statement reads. "At this point, our thoughts and prayers are with the families."

In the meantime, the air surrounding the facility was being tested Wednesday morning to determine if it's safe to enter, Ruiter said. Investigators from RCMP and WorkSafe BC will be investigating the leak, and the B.C. Environment Ministry, Interior Health Authority and a hazardous materials team from Calgary were also on scene Wednesday.

The city has declared a seven-day local state of emergency. Numerous homes in the downtown area were evacuated Tuesday afternoon, and up to 60 people received emergency social services, Ruiter said at the time.

An evacuation remains in effect for the area surrounding the arena, and affected residents are being offered accommodation at a local hotel.