About 800 people work at the Shell Canada refinery in the east end of Montreal. (Canadian Press)

Shell Canada is keeping the door open for last-minute offers to buy its troubled Montreal plant, even as the deadline for its closure approaches fast, leaving hundreds of employees at the waterfront refinery in the lurch.

Shell told employees earlier this year it planned to shut down the east-end refinery on June 1 at 5 p.m. because it wasn't profitable.

On Monday, the Calgary-based petroleum company said it had recently received a purchase offer from an unnamed company, but the terms were "unacceptable, and far from our expectations," said Shell spokesman Larry Lalonde.

Two other unnamed companies are said to be interested in the refinery, but Shell wouldn't provide any details before the Tuesday deadline. A teleconference between Shell and the potential buyers, was slated for Tuesday, but the oil company said it didn't want to create false hope that a solution could be achieved.

About 300 employees at the refinery are meeting with union representatives before the Tuesday deadline arrives, hoping another offer will materialize.

Union president Jean-Claude Rocheleau said workers who gathered at a meeting Monday were nervous about what could transpire.

"It's their bread and butter," he said.

Under union pressure, a committee headed by former senator Michael Fortier contacted about 100 potential buyers for the refinery from around the world. Montreal Mayor Gérald Tremblay urged Shell to give potential partners the extra time needed to conclude a deal for the site in the city's east end.

Quebec Premier Jean Charest said his government took steps to help find a new buyer in order to keep the refinery in business.

About 800 people work at the 76-year-old refinery, which is the largest one operated by Shell in Canada and processes at least 130,000 barrels of crude oil every day.

Shell said it wants to transform the plant into a distribution centre.

With files from the Canadian Press