MONTREAL - Time was precious at the Montreal Heart Institute on Wednesday as emergency crews struggled to pump 16,500 litres of diesel spilled last Friday. Concerns were raised as the clean up was taking longer than expected.

Neighbours of the research institute in Rosemont called the Montreal fire department over the weekend after a pumping truck mistook an observation well for a dedicated diesel tank, used to run the hospital's backup generators.

Emergency services responded to concerns about strong odours on Tuesday afternoon, pinpointing the hospital's parking lot as the sources of the smells.

"We don't want the diesel to remain in the environment and contaminate the soil," said Helen Proteau, the regional director of the Centre for Environmental Control. "It will depend on how much of the diesel can be removed over the next few days."

While the Canadian Press previously reported that 9,000 litres had been removed, Environment Quebec confirmed with CTV News on Wednesday that crews had managed to pump only 1,500 litres out of the ground.

"That was a really big mistake that they made, I'm worried about all the sick people in the hospital and if they can smell the fumes," said Mariette Larocque, a neighbour.

The hospital began installing ventilation towers on Wednesday to reduce the smell of diesel in the area.

"We've been assured by the fire department that there are no dangers to our patients or employees and that the investigation continues," said Gilles Lefebvre, an assistant director at the institute. "We have a messy situation that we need to clean up and we need to find the correct sequence of what happened."

Some of the diesel is believed to have seeped into the Montreal sewer system.