A toxic spill involving thousands of litres of oil at the Montfort Hospital will cost about $6 million to clean up.

Although the oil leak happened last January when a crane cut through a pipe near the new wing of the hospital, the hospital's board only informed the public about the spill at a board meeting last week.

Hospital officials say the Ministry of Environment was notified of the spill immediately and clean-up efforts began.

It will likely take 15 to 20 years to decontaminate the soil in the area. The cost will be covered by insurance.