Engineers are on the site of a leak at a Lower Mattagami Hydro project north of Kapuskasing.

They are trying to figure out what caused water to flood through a temporary dam earlier this week. They are also trying to determine if it's safe for workers to resume construction on the largest hydro project in northern Ontario in 40 years. The Kipling Project is one of four Lower Mattagami River hydro projects.

A trailer — where only two days ago workers were eating lunch — is now underwater.

No one was injured or in any danger, much to the relief of many, including the mayor of nearby Kapuskasing.

Al Spacek estimates 300 of his citizens are working at the Mattagami site.

"As a community were always concerned about their well being," he said.

"I'm very glad to hear no one was hurt in that event ... whether or not they're from Kapuskasing."

'It's going to take some time'

A spokesperson with Ontario Power Generation — the company building the dam — said it’s too early to tell what caused the leak, which occurred in a temporary dam set-up to keep river water out of a work area.

"People shouldn't be worried about the integrity of those structures at all," Neal Kelly said.

"Those temporary structures are checked every day by our contractor."

He noted engineers will decide when work can resume in that area and work can't resume until the area is drained.

"The engineers will look at it ... they'll assess what happened," Kelly said.

"It’s going to take some time. They'll come up with a plan on how they're going to fix it and move forward."

Kelly said work continues on the rest of the project and is ahead of schedule. The dam, which will produce roughly the amount of electricity needed to power Sudbury and Timmins at the same time, is expected to be open in 2015.