Two Toronto law firms say they'll file papers on Wednesday to start a $300 million class-action lawsuit on behalf of business owners and residents affected by this weekend's propane blasts.

The City of Toronto and Sunrise Propane Energy Group Inc., the site of Sunday's massive explosions, will be named on a notice of action, according to the website classproceedings.ca

The website states that the Toronto firms of Stevensons LLP and Bogoroch & Associates also "intend to commence an action against the Province of Ontario."

The Technical Standards and Safety Authority (TSSA), which carries out inspections on behalf of governments, is also expected to be named in the suit after it and the province receive a required 60-day notice, according to the site. The suit will be filed "in respect of the devastating propane gas explosions which occurred on August 10, 2008," said the website.

The suit is being launched "to hold the authorities accountable so it doesn't happen again," Harvin Pitch, counsel to Stevenson LLP, told CTV.ca on Wednesday.

"This shouldn't happen. When hazardous products explode someone is usually held accountable."

The class-action website states that one of the bases for the claim against the city of Toronto is that it "permitted Sunrise to locate and operate on the premises and to carry on its dangerous operation in the vicinity of residential homes and businesses."

"The plaintiffs claim damages in the amount of $300,000,000.00 for negligence, nuisance, trespass, strict liability," the website said.

Pitch said the suit could entail thousands of plaintiffs, but he noted that the $300 million compensation claim is "just a rough estimate."

"We won't know the accurate number until we get into the case," he said.

Thousands of Toronto residents in a 1.6-kilometre area were forced to flee their homes after a series of explosions went off at the Sunrise Propane Industrial Gases facility in the early hours of Sunday morning. The Sunrise facility was completely destroyed and homes and businesses in the area were damaged.

Local resident John Santoro, who is one of the people spearheading the case, said he and his neighbours just want fair compensation.

"At the end of the process, I just want to make sure that all of the people of the neighbourhood are dealt with fairly," he said.

"If they suffered any out-of-pocket costs, maybe through the class-action suit, they'll be able to be compensated for any losses that they may have suffered."

Most residents have now been allowed to return home, but six homes are still not considered safe because of possible structural damage. Residents in about 50 homes also remain shut out after asbestos, a hazardous material, was detected.

Woman dies after returning home

Meanwhile, there may have been another fatality linked to the blasts. Relatives and residents near the accident site said the stressful situation likely led to a heart attack suffered by 51-year-old resident Pat Loconte.

Loconte was allowed back inside her home on Wednesday, but she died a few hours later. Her sister-in-law said Loconte was "overwhelmed and shocked."

"She was not only my sister-in-law, but she was my best friend," Rosanna Loconte told CTV Toronto through tears.

Pat Loconte and her husband Joe operate a popular meat shop on Wilson Avenue. A sign posted outside the store informed customers about the death.

Autopsies were to be performed Wednesday on a firefighter who died fighting the blaze and a body found at the blast site. Church services and dedications for District Chief Bob Leek began with a mass in his honour Tuesday night.

Visitation hours at the De Marco Funeral Home on Keele Street were being held on Wednesday and Thursday. The funeral service will be held on Friday at the Prayer Palace on Arrow Road with full fire service honours at 11 a.m.

Parminder Saini, who works for Sunrise Propane Industrial Gases, has been missing since early Sunday. A body recovered at the site on Tuesday is believed to be his.

With reports from CTV Toronto's Chris Eby and John Musselman