* Signs of life including tapping had been detected
* Heavy cranes, mine rescue robotics on their way
* Prime Minister Stephen Harper offers federal help (Adds new comment from mayor, authorities; cuts number unaccounted for to 12)
June 26 (Reuters) - Rescue workers waited on Tuesday for specialized equipment to arrive at a collapsed shopping mall in the northern Ontario town of Elliot Lake, anxious to restart a three-day-old search for survivors as hope faded that anyone would be found alive.
"We all understand the urgency and the need to save anyone who may still be trapped beneath the rubble while keeping rescuers safe," Elliot Lake Mayor Rick Hamilton said.
Rescue authorities said the chance that anyone remained alive under piles of concrete and metal was "very slim," noting the last time any signs of life were detected was early Monday morning when audio equipment picked up sounds of breathing.
One person is confirmed dead and another is believed to have died in the collapse at the Algo Centre Mall in Elliot Lake, about 335 miles (539 km) northwest of Toronto.
At least 22 people were injured in the incident, none seriously. Police said 12 people were unaccounted for, a list that had shrunk from 30 earlier in the rescue effort.
" We still cannot determine how many people are there," Ontario Provincial Police Inspector Percy Jollymore told a news conference.
Authorities were focusing mostly on two missing people whose vehicles were found in the mall's parking lot.
Signs of life including tapping had been detected on Monday morning, but rescue crews suspended search efforts late on Monday because the two-story structure was deemed unstable.
Elliot Lake resident Gary Gendron said he believes his fiancée Lucie Aylwin, who worked at a lottery kiosk in the mall, is still alive under the rubble because the couple routinely tapped a code to each other to show their love.
"I know she's still alive," a tearful Gendron told Canadian Broadcasting Corp television. "As soon as she gets well we're going to get married."
Authorities had called off the search late on Monday after giving up hope of finding anyone alive inside the damaged portion of the mall, whose rooftop parking lot collapsed during busy afternoon shopping hours on Saturday.
But outrage from residents of the former uranium mining town and an appeal from Ontario Premier Dalton McGuinty persuaded officials to renew the effort.
CRANES, MINE RESCUE EQUIPMENT
Rescue experts said they were awaiting a large construction crane from Toronto that they would use to reach through the roof's hole and push an unstable escalator away from where victims are believed to be located.
Equipment would then be used to shear a path from the front doors to the collapsed section. The victims are believed to be 35 feet to 40 feet from the front door of the mall, authorities said. Dogs trained to locate both living victims and cadavers would then be sent in.
The collapse had sent at least one parked vehicle as well as concrete and metal raining into the mall below, opening a gaping hole in its roof.
The leader of the province said equipment including heavy cranes and mine rescue robotics were on their way.
"We will do everything we can to hopefully secure the building and allow (rescue workers) to get in there and get access to people who may be trapped there," McGuinty told a news conference in Toronto, rejecting suggestions that support has not arrived quickly enough to aid the rescue effort.
Prime Minister Stephen Harper has offered federal help, including the military, if needed.
Workers located a severed hand and foot in the rubble, authorities said on Sunday. The death was confirmed on Monday.
Numerous people have said the mall had a history of roof problems, including leaking ceilings and rusted beams that were reported to have been visible, according to media reports.
Overhead photos taken soon after the collapse showed several vehicles remained parked on the undamaged part of the rooftop lot. The collapse opened up a large, rectangular space and a clear view of the shopping concourse below. (Reporting By Andrea Hopkins; Editing by Frank McGurty and Eric Walsh)