What went wrong?

That's what everyone wants to know after two cops and three paramedics were injured after an explosion during a training exercise that went wrong in the west end on Wednesday.

It happened shortly after 10 a.m. along March Rd., at an abandoned house where "forced entry explosives" were being used during the exercise.

Dave Bowden was dropping his wife off at the Kanata Plastic Surgery & Cosmetic clinic across the street when he saw a swarm of police activity.

Then the explosion shook the clinic.

"I just heard a loud boom and a little bit of shaking to the building," said clinic receptionist Marie Little, who had been warned of training last week.

"It was like very loud thunder. The building shook."

Two of the paramedics, both men in their 30s who are "very experienced" in tactical training, were seriously burned but are expected to recover.

Despite wearing protective gear, they suffered second-degree burns to their hands, legs and other areas.

"There was a blast and flame," Ottawa paramedic chief Anthony DiMonte told a news conference. The paramedics were intubated as a precaution, and are in ICU at Ottawa hospital.

"They've been sedated. They're stable now."

Family of the injured paramedics were also at the hospital. The other three emergency responders all received minor injuries.

There were about 40 OPS and RCMP tactical officers at the exercise, alongside Ottawa tactical paramedics, who rushed to help their colleagues.

It is the first time Ottawa police chief Charles Bordeleau could recall such an incident.

"The training involved forced entry explosives, the use of minor explosive charges to facilitate officers to breach doors or windows," said Bordeleau.

"While the officers were doing that, that's when the incident occurred."

Such explosives are part of regular operations, and used by officers to forcibly enter homes, businesses or get access to other buildings.

This type of tactical operations practice, that often sees officers acting as suspects or victims, is not uncommon.

"They do this on a regular basis. Something went wrong," said DiMonte. "Obviously we all want to understand what happened as a result of this."

Multiple investigations are now underway, including the Ministry of Labour and the Special Investigations Unit, which probes police-involved incidents that have civilian injuries, which are the paramedics.

"Obviously the priority is around the injured officers and the injured paramedics," said Bordeleau. "That's who we're all thinking of. We want to make sure they're OK."

It is not unusual for police to use abandoned buildings for training exercises, with owner permission. Buildings such as abandoned schools have been used before.

A farmer who lives next door to the site said his family owns some of the property, but they weren't home at the time.

The site of the abandoned building where the explosion happened was bought by McDonald's and was supposed to be torn down for a new fast food restaurant, according to nearby workers.

The explosion led to a brief shutdown of some Hwy. 417 ramps and city streets for emergency crew access.

On average, the Ottawa police tactical unit responds to more than 100 high-risk incidents each year. It is police who request tactical paramedics on a call.

Danielle.bell@sunmedia.ca

Twitter: @ottawasundbell