Sodium hydroxide spilled into the Cheakamus River on Aug. 5, 2005, after nine CN freight train cars derailed near Squamish.

CN Railis facingfive charges related to a 2005 derailment near Squamish that spilled a toxic chemical into the Cheakamus River, killing hundreds of thousands of fish.

B.C. Environment MinisterBarry Penner said Friday that two charges were filed under the federal Fisheries Act and three under the B.C. Environment Management Act.

The Environment Management Act charges carry substantial penalties, Penner said.

"All of those charges separately carry a fine of up to $1 million, so potentially and theoretically, if convicted on all three counts, you could be looking at fines up to $3 million," he told CBC News.

The other charges relate to the destruction of salmon and their habitat, which fall under federal jurisdiction and carry penalties up to $300,000 each if the company is convicted.

The derailment caused 40,000 litres of sodium hydroxide to spill into the Cheakamus River from damaged railcars.

The chemical instantly made the water toxic, killing an estimated500,000 fish as it washed downstream.

An expensive restoration effort is still underway, with CN promising to pay millions to bring back fish and other creatures wiped out by the spill.

"I think everyone needs to be on notice that in British Columbia, we take our environmental laws very seriously," Penner said.

The B.C. Opposition's environment critic said charges brought against CN Rail for the Cheakamus Canyon spill don't go far enough.

Vancouver-Hastings MLA Shane Simpson, a New Democrat,said the province has to keep an eye on the company to make suresuch an accident doesn't happen again.

"We need a review now of safety on that line to ensure that in fact practices have changed, and in future, we're not looking at another Cheakamus River down the road," Simpson said.

In a report released last month, the federal Transportation Safety Board criticized CN Rail, saying it made several errors that led to the crash, and ordered the company to make a number of changes to the way it operates in difficult mountainous terrain.