Clean-up efforts were continuing Thursday near White River, Ont., where more than 63,000 litres of oil were spilled from a freight train after 22 cars came off the rails.

Canadian Pacific Rail revised its estimate of how much oil was leaked. Initial reports on Wednesday said about 600 litres of oil had leaked from the tank cars.

"The source of the now-discovered release of product from the second car was initially hidden as it was buried under snow. The product then migrated a short distance under the snow," said CP spokesperson Ed Greenburg.

"The additional spill was detected and the product was quickly contained as part of the railway's mitigation procedures. Soil and ground water sampling around and below the site is being conducted [Thursday].  There is no indication from any of the sampling sites that the product has migrated beyond the containment berms."

A spokesperson with Ontario's Ministry of the Environment said there is no risk to the health and safety of nearby residents, from the spill that took place east of White Lake Provincial Park, 10 km west of White River and 20 km upstream from Pic Mobert First Nation. The spill was only about 200 metres from the White River.

"Crews were able to get on the site and put down berms and dig trenches and take the appropriate remediation measures to prevent there from being an adverse impact to the natural environment," said Lisa Brygidyr, issues management co-ordinator for the ministry’s northern region

She said it's too early to tell if there will be any lasting environmental impact. 

"A spill like this one, depending on the migration and the quantity of materials that is spilled to the ground, can have impacts to the environment," Brygidyr said.

"But in this case, luckily the oil was pooled and it did not migrate toward the river. The spilled material was in a pooled area and any migration was going in the opposite direction of the river."

Train operation being evaluated

It could take anywhere from a couple of days to a couple of weeks for full assessment, she added.

"Our environment officer at the site is satisfied that work is being carried out to prevent any further impact and there is no health and safety threat at all from this derailment." 

Meanwhile, a crew from the Transportation Safety Board is investigating the cause of the derailment.

According to the manager for central regional operations for the rail/pipe branch with the TSB, a team arrived late Wednesday evening.

"They're in the process now of working through what they've seen and they'll be back there [Thursday] looking at some rail and some wheels of interest," Rob Johnston said, and noted they’ll likely have them on site until the end of the week, at which time they will reassess the situation.

"In every investigation we evaluate the operation of the train," he said.

"We will look at the condition of the rolling stock and we will also assess the condition of the track infrastructure."

At least one other tank car of oil is intact. Two tank cars with canola oil also leaked, but that leak is not considered dangerous.

CP rail said the rail line was re-opened Thursday evening after track repairs and inspections.