An explosion and fire at a manufacturing plant outside Montreal killed two people Thursday, authorities said.

The blast could be heard for miles and 19 others were hospitalized, some with severe burns. The two victims were found in the rubble of the decimated processing plant. The blast at the Sherbrooke, Quebec facility led to the fire, said police spokesman Rene Dubreuil.

Local fire chief Gaetan Drouin said there was at least one large explosion followed by a series of smaller explosions. He said the initial explosion set a local record for emergency calls to authorities.

Martin Carrier, a Sherbrooke police spokesman, said more than 100 people in Sherbrooke and surrounding suburbs phoned within a minute.

"They heard the explosion," Carrier said. "It was a big noise. A lot of black smoke. You could see it everywhere in the city."

About 50 firefighters were on scene. The plant lay in ruins and the only walls that remained standing were scorched black by the flames.

Firefighters probed the tangled building carefully, looking for potential victims. Among the 19 injured, four were transported to a burn unit in Montreal; two were in an intensive-care unit in Sherbrooke; seven were quickly released from hospital; and six were held for observation. The bodies were found later in the day.

Employees were evacuated from the plant within minutes of the explosion, and supervisors did a head count outdoors.

The plant belonging to Neptune Technologies & Bioressources produces and exports health products.

Environment Quebec, a provincial government body, said an initial toxicity concern stemmed from the plant's 3.9 gallons (15,000-liter) acetone reserves, which were struck by the fire. Acetone is flammable and, when ingested, can cause irritation.

However, officials said they were more concerned about the possibility of soil or water contamination than the risk associated with breathing the air near the blast site. Local health officials downplayed the toxic threat, suggesting people might potentially experience headaches or nausea but little else because of the smoke.

Police said it's unclear what caused the blast. Thick black plumes were seen rising from the facility.

The company called in a psychiatric support team to help traumatized workers. It promised to co-operate with police during the investigation.

"We're in terrible shock over what's happened," said Michel Chartrand, chief of operations for the company.

Shares of the company plunged 10 percent during a sell-off in less than a half-hour of trading following the incident.