The Canadian government did not adequately audit the railroad company at the center of the Lac-Mégantic crude tanker disaster, which last year killed 47 people, an independent federal agency said on Tuesday, as it called for tougher scrutiny of the rail industry.

The Transportation Safety Board of Canada, which issued its final report on what was one of North America’s deadliest rail accidents in recent memory, said a similar catastrophe could happen again unless more measures are put into place to boost rail safety.

Train shipments of crude oil have skyrocketed in Canada and the United States in recent years in the absence of sufficient pipeline capacity to transport the oil.

The TSB called for more thorough audits of safety management systems and said more physical defenses, such as wheel chocks or modern braking technology, are needed to prevent runaway trains.

The disaster occurred on July 6, 2013 after a single engineer parked his train or oil tankers for the night on a main line uphill from the small town of Lac-Mégantic, Quebec. The train rolled downhill after the brakes failed and it derailed, exploding in balls of fire and flattening the center of the town.

The TSB said Transport Canada, the federal transportation ministry, had failed to stamp out abuses at Montreal,Maine and Atlantic Railway Ltd (MMA), the now insolvent company that operated the train.

TSB Chair Wendy Tadros said MMA had a weak safety culture, trained its employees poorly, skimped on maintenance and did not have a functioning safety management system.

“Transport Canada knew about some of the problems at MMA, but the follow-up wasn’t always there. Instead, the focus was on making sure railway companies had a safety management system, not how they were using it,” she said.

“Transport Canada didn’t audit railways often enough and thoroughly enough to know how those companies were really managing – or not managing – risks,” she told a news conference.

The report could be politically damaging for the Conservative government, which is trailing far behind in the polls ahead of a federal election scheduled for October 2015.

Asked whether a similar disaster could happen again, TSB Chief Operating Officer Jean Laporte replied: “Unfortunately, right now, there are risks that that could happen.”

An official watchdog said last November that Canadian officials were not doing enough to ensure rail safety.

Transport Minister Lisa Raitt, pressed as to why her ministry had not shut down MMA before the disaster, said that was a matter for her bureaucrats to deal with.

She deflected repeated questions about government accountability and her own responsibility. Raitt, who did not receive the TSB report ahead of time, said she and her ministry would study it closely.

Ottawa has adopted several earlier TSB recommendations on improving the safety of transporting crude oil by rail, which Tadros said had occurred largely unchecked.

Greenpeace said the TSB report was “a searing indictment of Transport Canada’s failure to protect the public from a company that they knew was cutting corners on safety despite the fact it was carrying increasing amounts of hazardous cargo.”

In April, the Canadian government ordered that DOT-111 rail cars used for carrying crude oil be phased out by May 2017.

The U.S. Department of Transportation last month proposed new safety rules for hauling crude oil by rail. These included taking the older DOT-111s out of circulation within a maximum of five years.

TSB Chair Tadros said increased physical defenses are needed to stop runaway trains because not all operators will follow safety rules.

“Railways are high risk industries. We may not have thought of them like that before, but certainly (Lac-Mégantic) has taught us that,” she told Reuters.

The official opposition New Democrats blamed Ottawa in part for the disaster, saying it should not have granted an exemption to MMA allowing it to operate with just one engineer. (Writing by David Ljunggren in Ottawa; Editing by G Crosse, Chizu Nomiyama, Jeffrey Hodgson and Steve Orlofsky)