A US-based security company has sued Air Canada over gold bars and cash worth millions that were stolen from Toronto's airport in April. Brink's International alleges the airline was "reckless" and had failed to prevent the theft. The goods, worth more than C$20m ($15m, £12m), had recently arrived on an Air Canada flight from Zurich to Toronto before they were stolen. The heist is one of the largest in Canada's history. Among the items stolen were gold bars that weighed 400.19kg and $2m in cash. The April 14 theft garnered international headlines at the time, and it remains unsolved by the police. In the lawsuit, filed in the Federal Court of Canada on Oct. 6, Brink's said it was hired by a bank and a precious metal company to coordinate the shipment of the goods. The goods were stolen 42 minutes after they were unloaded from a plane that had just arrived in Toronto Pearson International Airport from Switzerland, the company said. After they were unloaded, the lawsuit alleged that an unidentified person gained access to the warehouse where the valuables were kept at around 18:30 local time. "No security protocols or features were in place to monitor, restrict or otherwise regulate the unidentified individual's access to the facilities," Brink's said. The person was allegedly able to enter by showing an airway bill for an unrelated shipment to an Air Canada employee. The airline then released the shipment to the individual, who "absconded with the cargo," the lawsuit stated. Brink's alleged that Air Canada staff made no attempt to verify the waybill's authenticity "in any way," and that the theft could have been prevented if Air Canada properly followed its security guidelines. The company argued that Air Canada is liable for the damages. Brink's has asked that the price of the goods stolen be paid back by the airline in full. Air Canada has not released a public statement on the allegations. The BBC has reached out to the airline for comment. The theft is one of the biggest heists in Canadian history. Other heists include the 2011 and 2012 Great Canadian Maple Syrup Heist when 3,000 tons of syrup valued at $18.7m were stolen from a storage facility in Quebec. — BBC