A large quantity of a chemical fertilizer, which can be used in making an explosive bomb, is unaccounted for just weeks before the G8 and G20 summits, and now police are searching for the man who purchased it.

Niagara Regional Police says a man bought more than 1,600 kilograms of ammonium nitrate late last month from a gardening shop in Lincoln, Ontario.

Ammonium nitrate could be used for powerful bomb-making. An explosive made with this material was used in the 1995 Oklahoma City bombing that killed 168 people.

The man gave staff the impression he was a regular customer, but they later found out that wasn't the case.

He's described as being 40 to 50 years old with missing fingers on his right hand. He may be of European decent and walks with a slight limp.

The 2008 Explosives Act requires that the sale of ammonium nitrate to be recorded, and buyers are supposed to provide identification. The act was passed after the 2006 arrests of the so-called Toronto 18 – a group accused of plotting terrorist acts in Toronto.

The Minister of Public Safety is aware of this investigation, and a spokesperson tells CP24 the following:

"The safety and security of Canadians is of the utmost importance. That is why this government invests in the measures appropriate to make sure our communities are safe, including ensuring we have the best security plan in place for the upcoming G8 and G20 summits. The Minister has been briefed the ongoing investigation led by the Niagara Regional Police Service. The RCMP is providing assistance as requested."

CP24 will be airing a live news conference at 4 p.m. as police address concerns of a possible bomb threat ahead of the G8 and G20 summits.

Anyone who can help police track down the missing fertilizer can call authorities at 905-688-4111 or leave an anonymous tip with Crime Stoppers at 1-800-222-TIPS.