Two security guards were injured by an explosion Thursday during an armed robbery inside a bank in north Edmonton.

The security officers were delivering money to an ATM inside Scotiabank at 8140 160th Ave. at 2:10 a.m. MT when an "explosive device" was detonated, said Edmonton police Staff Sgt. Paul Czerwonka in an interview with CBC News.

There was a confrontation between a suspect and one of the guards, Czerwonka said.

The robber, who was armed and wearing a disguise, ran from the scene with "money in hand," Czerwonka said.

The suspect remains at large. Scott Pattison, a spokesperson for Edmonton police, said it's not known if the suspect is male or female.

'A pretty bad situation'

The guards, a man and a woman employed by GardaWorld, were taken to hospital with non-life-threatening injuries. The woman has since been released.

Teamsters Canada, the union that represents the guards, said in a news release an improvised explosive device (IED) injured two guards.

Union representatives said in a statement that IEDs are uncommon in armoured car robberies, with knives or guns more commonly used.

Representatives called the ambush "gutless" and "cowardly."

"Armoured car crews are professionals who put their lives on the line every day, but they don't expect to face IEDs when they go to work," said Al Porter, secretary-treasurer of Teamsters Local Union 362, the union representing most armoured car guards in Alberta.

"The two guards did everything right last night."

Wayne Garner, president of Teamsters Local Union 362, said the incident is alarming for members of the security industry.

"How do you even imagine or justify that someone would use an explosive device for a robbery like this?" Garner asked during a news conference near the scene.

"So I understand there are going to be a lot of questions asked.

"Was the bomb used as a means to just divert or was the bomb actually used as a weapon?

"It shows you that this individual who decided to do this has no concern whatsoever about the lives that are at stake here."

Garner said the employer did "everything right," and the union will not be calling for any changes in protocol.

However, he believes the incident will prompt changes in how guards are trained for the job.

"I'm just so thankful that these folks are okay," Garner said.

"The injuries were significant, physically, from what I can see from the photographs," Czerwonka said.

"There was definitely significant injuries to the male guard, to his head and his scalp, potentially his skull. I don't know how deep his wounds are, but they're pretty significant."

As of 6:30 a.m., a bomb unit and forensic investigators were en route to the scene, Czerwonka said. Drivers were being asked to avoid the area.

"We don't even have a clue because the bomb guys haven't done their search yet," Czerwonka said.

"I don't believe it was an accident. I think it was a device meant to make the guards, make them not able to respond so they could grab the money and run. I think it was intentional.

"It's a pretty bad situation. We're still investigating."

Police say two security guards were delivering cash to an ATM when a blast went off inside the bank. (David Bajer/CBC)

'Very, very loud'

Kevin Uchman, who lives across the street from the bank branch, said he and his wife were startled awake by the sound of the blast.

"The best way I can describe it is like a big garbage bin being dropped," Uchman said Thursday morning.

"If you can imagine the big front-end loader trucks when they drop their bins ... it sounded like it was being dropped from 20 feet.

"It was very, very loud."

Initially, Uchman said he thought the sound was the clatter of a dump truck emptying garbage bins at the strip mall nearby.

"I shrugged it off," he said.

Uchman and his wife went back to sleep, but when they woke up about an hour later to let their dogs out, the area was teeming with police.

Uchman said he has acquaintances who work at the bank, and news of the hold-up has left him feeling rattled.

"For something like this to go off in your own backyard, it was a little unnerving."

Kevin Uchman describes an explosion at a bank in his neighbourhood. 0:32

In an emailed statement, GardaWorld's director of marketing and corporate affairs Isabelle Panelli said the company is working with investigators.

''Our employees are now safe and in good hands," Panelli said in the statement. "We are providing support to our employees, their families and colleagues at the branch.

"GardaWorld's corporate security team is collaborating with the local authorities [in] the investigation.''

There was a heavy police presence on scene Thursday morning. Police tape encircled the bank where a GardaWorld armoured truck could be seen parked adjacent to the front entrance.

In an emailed statement, Scotiabank said the company is taking the incident "very seriously."

"We are thankful that our partners' employees are now safe," Scotiabank spokesperson Doug Johnson said in the statement.

"Our primary focus is on the well-being of our employees at this time and we have been in contact with the branch to ensure they have all of the support they need.

"We are working with authorities during their investigation, and we encourage anyone with any information to contact the Edmonton police."

Police responded to a similar case in September when an improvised explosive device detonated inside the vestibule of an RBC branch near 27th Avenue SW and 141st Street in southwest Edmonton.

Guards had just arrived at the bank "to perform their regular duties" when a loud bang startled them, but no money was taken, police said.