TORONTO - Police have yet to identify a man who under false pretences bought enough fertilizer to make a bomb, at a store not far from where the G20 summit will be held.

The Integrated National Security Enforcement Team released a composite sketch of the man Wednesday, appealing for any information about who he is.

"The individual who made the purchase falsely misrepresented himself as making the purchase on behalf of a local grower," said Insp. Gord Sneddon.

"That, candidly, is somewhat suspicious."

While Sneddon stressed there was no evidence the purchase was related "in any way" to the G20 summit in Toronto, he said the man's behaviour needed explaining.

"Why would he try to conceal his identity? We don't know."

The man, believed to be in his late 50s or early 60s, bought the ammonium nitrate in the mid-afternoon of May 26 at a farm-supply store in Lincoln, Ont., about 100 kilometres from Toronto.

Store workers reported the purchase to regional police on May 31.

While the product is a legitimate agricultural fertilizer, it has also become a substance of choice for terrorists, since it is readily available and can be converted into an explosive.

Timothy McVeigh used an ammonium nitrate bomb to kill 160 people at a federal building in Oklahoma City in 1995.

More recently, several Canadians have been convicted of terrorism-related offences for planning to build fertilizer bombs, while insurgents in Afghanistan use them to deadly effect against coalition forces.

"You don't need a lot of ammonium nitrate to build an explosive device," Sneddon said. "That's why we're concerned."

Police said it was also possible the purchase was related to a marijuana grow-op.

The man was described as short and stocky, with missing fingers. They said he walked with a limp, had brown unkempt hair, and talked with a strong accent.

Sneddon refused to confirm exactly how much fertilizer was bought from Vineland Growers, saying only it was a "large quantity" but that it would not service a large farm.

Earlier reports said the man drove off with 60 25-kilogram bags — a total of 1,500 kilograms.

Regulations require sellers to identify people buying ammonium nitrate. Why that apparently didn't happen in this case was not immediately clear.

"Not every effort that should have been taken (to identify the buyer) was taken," Sneddon said.

The composite sketch was based on information from three witnesses.

A few months ago, police believed two tonnes of fertilizer had disappeared before the Olympic Winter Games in Vancouver.

It turned out to have been a counting error.