RICHMOND, B.C. (CP) - CN Rail is facing more questions after two derailments in a single day, including one on the trouble-prone former B.C. Rail line north of Vancouver and another that sent a car loaded with new automobiles into the Fraser River.

The accidents happened within hours of each other on Monday, and while CN (TSX:CNR) said there is no evident connection, critics want federal regulators to take a closer look at the railway's record and rail safety overall. The first accident took place Monday afternoon when seven empty cars of a 125-car train jumped the tracks in the Cheakamus Canyon north of Squamish, B.C.

It's the same stretch of former B.C. Rail line where a tank car loaded with a caustic soda broke open after plunging into the Cheakamus River last summer, causing a serious fish kill.

CN, which acquired the B.C. Rail operation from the provincial government in 2003, has experienced 11 derailments on the line so far this year.

On Monday evening, four cars of a 39-car northbound train carrying new autos derailed while crossing a swinging trestle over the Fraser River into the Vancouver suburb of Burnaby from an industrial area in neighbouring Richmond.

"The train was almost across the bridge," said Graham Dallas, CN's regional communications manager. "Three of them derailed upright on the bridge. The last car in the train, however, fell off the bridge into the water."

The surviving derailed cars sat stranded at the north end of the bridge while CN workers and employees from salvage and environmental-response contractors worked on the wreck site.

A containment boom surrounded the submerged car near the riverbank while a massive crane on a barge prepared to lift it.

Dallas said there's no real environmental concern.

"Those are largely in place for when we lift the rail car out of the water," he said. "As we lift it out we want to have the booms around it just as a precaution in case there is any leakage of any product from any of those cars."

Dallas would not speculate on the cause of this accident. He said the track and trestle is inspected weekly, sometimes on foot, and unlike the accident-plagued former B.C. Rail line, CN has owned this line for decades.

The speed limit for trains crossing the trestle is 16 kilometres per hour.

The railway is at a loss to explain the spate of derailments in British Columbia, said Dallas.

"Certainly it is unusual," he said, adding CN is considered the safest railway in North America. "We've taken great pride in that so we're very concerned about the number of accidents."

The company's worst accident this year spilled 700,000 litres of oil and potentially hazardous wood preservative into a Wabamum Lake near Edmonton on Aug. 3, two days before the Cheakamus River spill.

Besides facing a $28-million cleanup bill, CN suffered a public-relations black eye when it initially didn't inform residents aiding the cleanup that the spill could be toxic.

A report issued Monday by an Alberta commission into the accident recommended the province adopt tougher environmental legislation to help prevent similar disasters.

B.C. Transportation Minister Kevin Falcon noted railways are a federal responsibility but said regulators in Ottawa must understand B.C. residents are concerned about CN's operations, "particularly on the former B.C. Rail line.

"We expect the federal regulator to take whatever steps are necessary to restore public confidence," he said. "That's the message that I've been giving to the federal regulator."

A spokeswoman for federal Transport Minister Jean Lapierre was unavailable for comment.

But Industry Minister David Emerson said Lapierre is "vigilantly looking" at CN's operations, including its procedures and the former B.C. Rail line itself, to see if the railway complies with operating requirements.

Emerson said he is extremely concerned with the number of CN derailments, especially on the line it acquired from B.C. Rail, which he noted was in serious financial trouble before the takeover.

He speculated the Crown-owned railway "was probably not able to put the kind of capital expenditures into maintenance and upkeep of the line as a strong, well-capitalized railway ought to do. I suspect CN is running into some deferred-maintenance issues."

Critics have pointed to the increasing length of trains since the B.C. Liberal government sold off the B.C. Rail operation to CN for $1 billion.

Lapierre last month ordered CN to cut its trains on the most troublesome stretch of the line to 80 cars from upwards of 120.

The rule applies to trains with locomotives only at the front. If so-called pusher engines are located in the middle of the train there is no upper limit to the length, said Dallas.

The train that derailed in the canyon Monday had four locomotives at the front and two in the middle.

"We were in full compliance with the federal order," said Dallas.

But David Chudnovsky, the NDP's transportation critic in the provincial legislature, said the restriction should be expanded to limit all CN trains to 80 cars until its operations are reviewed.

Unionized employees of CN have said that the company's safety record has declined since it was privatized in 1995 and it has cut staff steadily.

Conservative transportation critic James Moore said train-length limits are reasonable but don't go far enough.

"The overall problem that we have is that federal regulations that are imposed on Canada's rail operators are not being followed through on and they are not being properly enforced by the federal government," said Moore, campaigning for re-election in his suburban Vancouver riding.

Moore said the Liberal government has ignored his party's calls for a comprehensive safety review.

Emerson played down the need for a full review but suggested a more focused investigation might be more cost effective.

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