© The Canadian Press / Dave Chidley
A firefighters holds a hose on the scene of a three story apartment building fire in Woodstock, Ontario, Sunday, March 27, 2011. Seven people were taken to hospital and up to 11 more are unaccounted for, police said.
Seven people remain unaccounted for after a fiery explosion reduced an apartment building to a pile of bricks and charred wood in Woodstock, Ont., on Sunday.

With a large part of the three-storey building now turned to a pile of smoldering rubble, police said the outlook for those missing was grim.

"If we don't have any fatalities, I'll be very surprised," Sgt. Marvin Massecar of Woodstock police said late in the afternoon.

Raging flames tore through the building after nearby residents reported hearing a thunderous explosion and feeling the ground shudder early Sunday morning. Plumes of black smoke could be seen from the distance as fire crews worked to douse the blaze.

At one point, it looked like much of the building's facade was consumed by roaring orange flames, which caused the structure to crumble into a heap of bricks and twisted metal.

Seven people, including a firefighter, were injured in the blaze, police said. Six of those hurt were treated at Woodstock General Hospital and released. One person remained in hospital with non-life-threatening injuries.

By Sunday evening, police had taped off a large area surrounding the building and evacuated all the homes on Victoria Street.

The Office of the Fire Marshall and Ontario Provincial Police were on scene, but Woodstock police said the building was not safe to enter.

"When it's safe to go in, we're going to investigate," said Const. Steven McEwen.

"I haven't seen a residential fire like this in my time on the job," added McEwen, who has worked as a police officer for roughly 20 years.

About 30 firefighters were called in to battle the blaze, which caused the middle portion of the building to collapse entirely, he said.

Officials said the building contained 36 units, although some were unoccupied.

Resident Lance Bicknell said police officers helped him and his wife climb down from their third-floor balcony.

Inside, "smoke was so thick, you couldn't see the walls," he told Toronto TV station CP24.

Another third-floor resident said he woke up on the first floor after the building had collapsed. He said he didn't understand how an explosion occurred because the building used electric heat.

On Sunday evening, area residents stood atop a nearby overpass and gazed at the back of the gutted building. One onlooker, who said he was able to get fairly close before police tape went up, said the front of the building was missing entirely.

Meanwhile, several dozen displaced residents had been transported by the Red Cross Society to an undisclosed location.

Earlier in the day, they received food and drinks from the Salvation Army at a nearby Via Rail station.

Lisa Woods, a spokesperson for Woodstock fire, said some residents had also been put on buses at the scene to wait for information on their units, while others went to a nearby Red Cross facility or to stay with family.

Donna Holst, 50, lives in an apartment above an animal hospital across the train tracks from the building. She said she heard the explosion from her home.

"We didn't know what the noise was," said Holst. "We thought it might have been from the animal hospital down below, and then realized when we saw the smoke outside the window that it was not."

Holst said she felt "shocked" and "afraid for all the people in the building" when she saw the thick, grey smoke.

She knows three residents of the building and said two were safe. She had not heard anything about the third, an elderly woman on the bottom floor.

The building's residents include a number of seniors and some low-income families, Holst said.