TORONTO -- More than 1.5 tonnes of marijuana was found in a truck entering the U.S. from Canada, American border officials allege.

U.S. Customs and Border Protection (CBP) says the 1,517-kilogram stash was seized on June 13 from a truck that had tried to cross into New York state from southern Ontario, carrying 58 cardboard boxes supposedly full of peat moss.

Authorities say the marijuana was likely destined to be sold on the streets of major cities on the American East Coast, where they estimate that it would have been worth US$5 million.

Gurpreet Singh, a 30-year-old man from India, was arrested at the border and will face charges of unlawfully importing marijuana and possession of marijuana with the intent to distribute. If convicted, he will face a mandatory prison sentence of 10 years.

Authorities say another large pot bust was made eight days earlier at the same crossing – the Peace Bridge linking Ontario's Niagara Region to Buffalo, N.Y. That seizure allegedly involved more than 800 kilograms of marijuana.

The June 13 seizure, which was announced Tuesday at a press conference is the largest-ever made by CBP agents in the Buffalo area, according to Rose Brophy, the director of the agency's Buffalo office.

Although the Canada-U.S. border has been closed to all but essential traffic since March due to the COVID-19 pandemic, American officials say they have seen an uptick in illegal drug activity there.

Even if the two large seizures were not part of the equation, the weight of illegal drugs seized by border guards in the Buffalo area since the closure would be nearly 20 times what it was during the same period last year. Most of the drugs seized have been marijuana.

"The criminal organizations are always going to continue to exploit whatever they can," CBP spokesman Aaron Bowker said at the press conference.

With files from CNN