More cocaine has been seized entering Canada at the Ambassador Bridge than at any other land border crossing in the country.

During the last six years, the Canadian Border Services Agency made 13 cocaine busts at the international crossing in Windsor, according to statistics obtained by CBC's Power and Politics through Freedom of Information. The drugs were worth $91.5 million.

More busts were made at four other border crossing, but none worth more in totality than Windsor.

Crown attorney Richard Pollock has prosecuted many of the recent smuggling cases. He said the increasing strength of the Mexican drug cartels are fuelling the increase.

"We're not as far away as we really think," he said of the drug cartels. "The transportation hub appears to be in California and Texas, land crossings using commercial trucks."

Geography that puts Windsor right in the centre of a very lucrative and dangerous drug trade, running from the southern U.S. to Montreal.

"We know that that cocaine is coming through our border but it's being distributed throughout the country," Windsor police spokesperson Sgt. Matt D'asti said.

At the Windsor-Detroit Tunnel, the type, number and value of drug busts differ from those at the bridge.

Agents there made 495 seizures, fifth-most in the country during the same time frame. Marijuana was seized most often. It accounted for $48,000 of the $86,000 worth of all drugs seized at the downtown Windsor crossing.

Drug busts by the CBSA rose 10 per cent between 2007 and 2012, according to a CBC News analysis of agency data.

Some say is just a fraction of a multibillion-dollar flow of illegal drugs into Canada. Critics fear Canada is about to take a step back in its war on drug smuggling due to a shift in focus and budget cuts to border security.

The union representing border agents in Windsor said the numbers provided by the CBSA don't tell the whole story.

"I believe that if we weren't faced with the kind of staffing shortages, the kind of resource limitations that we [face], I certainly believe we would be stopping a significantly higher amount of contraband at these border points," said Jason McMichael, who speaks for the Customs and Immigration Union.

Police are also concerned. If millions of dollars worth of drugs are being seized at the border, they wonder how many are getting through and onto the streets.

"Any time people are transporting illegal drugs it can be a concern, for sure," D'asti said.