A train carrying crude that derailed in northern Ontario, Canada, spilt 100 time more oil than initially reported, bringing the total to about 400 barrels, according to rail operator Canadian Pacific Railway.
The railway had initially reported a spill of about four barrels. The figure increased because the extent of the spill was not apparent when crews first arrived at the site of the train wreck near White River, Ontario, about 700 kilometers north-east of Toronto, a spokesman said.
"During the clean-up yesterday our crews discovered the second derailed car containing oil had in fact lost product," Reuters quoted Canadian Pacific spokesman Ed Greenberg as saying. "The second car was difficult to assess due to its position among the derailed equipment but showed no signs of the product around its base during the initial assessments."
The spill is Canadian Pacific's second in a week. The updated figure makes the spill worse than the one reported last week in the US state of Minnesota, which occurred when 14 cars of a 94-car train derailed, spilling about 357 barrels.
The Ontario derailment occurred on Wednesday when 20 cars on an eastbound, mixed-freight train bound for Montreal left the tracks. The spill has been contained, Greenberg said. An investigation into the cause in ongoing.
The spills come amid a boom in North American oil production that has strained pipeline capacity. Operators in high-producing areas that lack transportation infrastructure have turned to rail to get oil to market.
The incidents also stand in juxtaposition to a high-profile spill in the US state of Arkansas, which occurred when an ExxonMobil-operated pipeline ruptured and released up to 5000 barrels of heavy crude into a residential neighbourhood.
A debate is raging in North America about oil transportation, as the fate of the contentious Keystone XL pipeline from Alberta to Texas hangs in the balance. Opponents of the pipeline point to the Arkansas spill as evidence the TransCanada project is too risky.
Many experts point out that other transportation methods, such as rail, are more dangerous than pipelines, a claim underscored by the latest spills.
The Minnesota and Ontario rail spills are the first major incidents since producers have migrated to that form of transport.
"I think rail is now going to face the same kind of scrutiny that pipelines have come under," Keith Stewart, a spokesman for Greenpeace Canada, told Reuters.
"Rail used to be pretty inconsequential in terms of moving oil, but we've seen rapid growth in the last three years and they're projecting massive growth. I think the industry has rose-coloured glasses on if they think that they can ramp up moving oil by rail, the way they're talking about, without running into big opposition."