Police released three variations of a composite sketch of the suspect who purchased the ammonium nitrate on Wednesday.

Inspector Gord Sneddon, a Toronto police officer who heads up the RCMP’s Integrated National Security Enforcement Team for the coming G20 summit, described the purchase as “puzzling.”

“Why would he try to conceal his identity?” Sneddon asked.

Investigators have been unable to identify the man and don’t know if the purchase was made for nefarious reasons, for a marijuana grow op or for the legitimate purpose of local farming.

Sneddon said the quantity was not out of the ordinary for agricultural purposes.

“It has been used in the past as a basis for an explosive device, but it may have been purchased for another purpose. We’re not interested in a marijuana grow op, our interest is the security concern.”

He urged the mystery man to contact police.

Sneddon would not confirm how much fertilizer is unaccounted for, nor address reporter questions about it being more than the amount used in the 1995 Oklahoma City bombing.

Police say the man, who is about 50 years old and white, walks with a slight limp and is missing two fingers on his right hand. His identity remains unknown.

The investigation into his identity is still in the hands of the RCMP’s Integrated National Security Enforcement Team.

With the G20 and G8 summits around the corner, the police said they’re taking no chances.

“It is a legitimate fertilizer in that quantity, it’s just that it is also an ingredient for a bomb,” said RCMP Sgt. Marc LaPorte. “There is a concern because of the upcoming events in Huntsville and Toronto. We’re taking this potential threat seriously.”

The large fertilizer purchase was flagged because the supplier, Vineland Growers cooperative farm centre in the town of Lincoln, didn’t get the man’s identification details after he gave the impression he was a regular customer.

Regulations require anyone who buys ammonium nitrate to be identified.

David Lepp, manager of operations for Vineland Growers, declined to comment on whether the mystery buyer was picked up on one of his firm’s many security cameras.

He’s also declined to answer any questions on the purchase including whether the man paid for the fertilizer with cash or a credit card.

“There is an ongoing police investigation,” Lepp said.

Police are looking for the man who bought 60 25-kilogram bags of ammonium nitrate fertilizer in Lincoln, Ont., on May 26.

Authorities were not notified until May 3, when the vendor became suspicious.

Lincoln is more than an hour’s drive from Toronto.

The police are now asking for the public’s help in finding the man after initial canvassing of the region failed to provide any concrete leads.

“Right now we’re trying to take the necessary steps to locate that individual and confirm that it was purchased for fertilizer,” said LaPorte.

Ammonium nitrate-based explosives were used by U.S. bomber Timothy McVeigh in the 1995 Oklahoma City bombing.

McVeigh packed more than 1,000 kilograms of the substance into a truck and detonated it at a federal government building in Oklahoma City, killing more than 160 people and injuring more than 400.

Bombs made with ammonium nitrate are the largest killer of allied troops in Afghanistan.

In November, 2006, police foiled an Al Qaeda-inspired plot to blow up buildings in downtown Toronto with fertilizer-based bombs in a case known as the Toronto 18.

In the Toronto 18 case, two men were arrested after buying 125 25 kg bags of ammonium nitrate.

*With files from The Canadian Press