An ammonium nitrate stockpile exploded last week in Beirut killing at least 171 people, injuring 6,000 and leaving a quarter of a million people homeless.

Nutrien, the world's biggest fertilizer maker by capacity, produces ammonium nitrate at Redwater, Alberta, and sells it to customers in the mining industry, CEO Chuck Magro said in an interview. The company does not sell ammonium nitrate for agricultural use, and the industrial chemical is a small part of the company's overall business, he said.

"I strongly believe that what we're doing here to produce this product, that is needed for the mining industry, is very well-handled in Canada," Magro said.

Some of the world's deadliest industrial accidents have involved ammonium nitrate, including a 2013 explosion at a Texas fertilizer plant.

The U.S. Chemical Safety Board, an independent federal agency, said in a statement on Friday that regulatory changes in the United States are necessary to prevent future catastrophes.

Nutrien's ammonium nitrate is stored under 24-hour surveillance and monitored by heat detection systems. There are restrictions on how much can be stored in a location, Magro said.

Nutrien spokesman Will Tigley said the company does not store ammonium nitrate outside its plant and has tracing protocols for all shipments.

Lebanese authorities said 2,750 tonnes of the industrial chemical had been stored for six years at Beirut's port without safety measures.

Experts say the Beirut explosion should be a wake-up call for countries regarding the dangers of ammonium nitrate.

Quantity, ventilation and proximity to flammables are seen as critical, as is distance from population centers.

By Rod Nickel