Police are telling people in Woodstock to brace themselves, as two people remain missing a day after a blast and fire at a 45 unit apartment building.

Two seniors who lived in different units in the central portion of the three story complex, Margaret Gillett and Bill Watmough, are unaccounted for.

Gillett's nephew Stephen says the family knew something was wrong within hours of the fire, "There was no sign of her anywhere, not with the Red Cross, not at the hospital, not at any of the places where she usually goes."

Meanwhile Watmough's wife reportedly escaped the blaze and was taken to hospital with minor injuries.

Seven people and one firefighter were taken to hospital with non-life threatening injuries immediately after the explosions and fire. Seven people were initially unaccounted for in the confusion, but five were later located.

Woodstock Police Chief Rod Freeman says "I can tell you right now that the number of people that are currently unaccounted for stands at two. Given that information and given the fact that 24 hours has passed I think we should prepare ourselves for what could be a tragic day today."

Police say right now there's no evidence of a criminal act in the incident. The Ontario Fire Marshal and local investigators are at the scene. The investigation is in the preliminary stages so no cause has been confirmed.

At a press conference Monday afternoon police said emergency workers were using heavy equipment to move the rubble, but it's a slow process.

Woodstock Police Cst. Steve McEwan says "Our forensic identification officers are on scene and they will continue a systematic search of the rubble."

The Fire Marshal's Office says they are still trying to determine a fuel source for the explosion, but they must dig through layers of debris. They say they will be examining natural gas system and gas appliances including dryers, but nothing has been confirmed.

Meanwhile, residents continue to speculate about what may have been behind the explosion.

Tenant Rob Earl says "I talked to a few people when I came down after it happened and a few of the people I was concerned about I talked to and they said that they could smell gas early in the early morning…it's just a tragedy and it was an accident so carry on from there."

Earl told CTV News the apartments themselves all had electric baseboard heat, while the common areas like hallways and the laundry room were heated by a forced air gas furnace.

Residents trying to recover

More than 100 people were displaced by the fire, including residents of the Wellington Street complex and those evacuated from nearby homes.

Building resident Paul Gibbon was asleep at home when the explosion happened.

He says "There could have been a lot more when you look at that building when you got out the walls were blown out and everything. There could have been a lot more people in there. There are 36 apartments in that area, some of them got out pretty messed up."

About 30 to 35 residents left homeless are being helped by the Red Cross, and permanent shelter options are being worked out.

Cindy Gale and her husband got out in time, she says she's "numb, empty, just trying to keep busy and not dwell on it too much."

But she is thankful for those that got out, "We can replace that stuff in the apartments, but we can't replace each other."

Those evacuated from homes on the east side of Victoria Street are being allowed to return to their homes after 8 p.m. Monday night.

Class-action lawsuit being launched

Windsor, Ont. law firm Sutts, Strosber LLP and Toronto area firm Falconer Charney LLP are reportedly already organizing a class-action lawsuit on behalf of the building's residents.

The announcement comes despite the fact that the investigation is ongoing.

A meeting will be held Tuesday afternoon for residents interested in being involved in the lawsuit, which is expected to be filed by the end of the week.