Four people were taken to trauma centres with life-threatening injuries on Tuesday morning following a gas explosion at a North York condo under construction.

Three other people suffered minor injuries and were also taken to hospital following the explosion.

Toronto Fire confirmed all seven people were working at the building, in the Esther Shiner Blvd. and Provost Dr. area.

Emergency services responded to a 9:15 a.m. gas explosion in the boiler room at the penthouse level, officials said.

“On arrival there was no fire here but crews were met with multiple patients and initiated requests for EMS units to attend,” Toronto Fire Services Paul O’Brien told reporters at the scene.

“We had patients exhibiting signs of burns but there was no fire on TFS arrival.”

Roads in the area were closed and Toronto Police, Toronto Fire and the Ministry of Labour were investigating the cause.

“I can’t speak to the exact nature of the injuries due to privacy constraints,” said Toronto EMS Chief Bikram Chawla at the scene.

O’Brien said it was very rare to be called to an accident like that on a building under construction.

“We do not attend a lot of calls like this, of this serious nature, in construction sites,” said O’Brien. “But I cannot recall in the last couple of years something to this nature.”

RECOMMENDED VIDEO

He didn’t know how many workers were on the site when the explosion occurred or when the building could be cleared for work to continue or if any residents were actually living there at the time of the explosion.

“The investigation is just in the initial stage so I’m not sure when the (workers) will be able to get back into the building,” he said.