ST. CHARLES — An ammonia tank burst inside a burning meat processing plant in this southeastern Minnesota city Friday night, hours after authorities evacuated the town of about 3,600 as a precaution, police said.

Police Chief Bill Eckles said he got word from the command center around 8 p.m. that one of the anhydrous ammonia tanks in the North Star Foods plant had burst, and that a low-hanging vapor cloud might be visible.

The police chief said he had no immediate information on the extent of the leak, or whether it posed a threat to firefighters at the scene or anyone else. But residents waiting in an evacuation center at St. Charles Borromeo Catholic Church on the edge of town were advised to stay inside.

City Administrator Nick Koverman said there were about 30,000 pounds of anhydrous ammonia in five tanks in the plant. The refrigerant can cause severe burns, particularly to the eyes, throat and lungs. The cause of the fire wasn’t immediately known, he said, and it wasn’t clear when residents would be allowed to return.

Civil defense sirens blared to warn residents to get out. Sheriff’s deputies began door-to-door evacuations of people and pets about 3:30 p.m., and evacuation centers were set up for displaced residents at the church and schools in nearby communities. Both major highways through town were closed.

“I can’t give you a time frame on when you’re going to be allowed to go home,” Winona County Deputy Rod Hansen told over 100 residents who gathered Friday night at the church.

A hazardous materials team from Rochester was summoned as smoke poured from the sprawling building. Firefighters from surrounding cities converged to help fight the blaze. Eckles said earlier that a few firefighters suffered some smoke inhalation, but there were no immediate reports of serious injuries.

Smoke from the fire could be seen 10 miles away by late morning, and by late afternoon three tornado-like clouds of gray smoke were visible from five miles away. Hansen said that by nightfall the flames were no longer visible outside the plant.

North Star Foods plant manager Mark Eads said the fire started late Friday morning above one of the ovens where chickens are cooked.

“Within two to three minutes, there was smoke coming out of the room pretty heavy,” Eads said.

Carolyn Nicklay, who works in human resources for the company, said she called 911 and firefighters quickly arrived.

“Everybody’s out. Everybody’s OK. That’s all that matters,” she said.

The Rev. Bill Cronin of St. Charles Borromeo drove through the center of town about 12:30 p.m. after celebrating Mass at a nursing home, before the evacuation order. He said the smoke was “really black and acrid-looking. ... You could almost smell the toxins in the air.”

The nursing home residents were taken to Rochester, while some people from an assisted-living home were brought to the church, where Red Cross workers were rounding up cots for anyone who decided to stay the night there. Cronin said he was amazed at the well-organized response by emergency officials.

“If something can go very well, this went very well,” the priest said.

North Star Foods is the second-largest employer in St. Charles with about 150 workers. Their futures were on the minds of some residents even as the fire burned.

“They might all lose their jobs,” Amber Kesler, a customer at the Good Sport Bar and Grill, said before the evacuation was ordered. “And the way the economy is going, you don’t want to lose your job.”

Locally owned North Star Foods Inc. has been in business since 1971, serving industrial, retail and foodservice customers, according to its Web site. Its products include chicken, turkey, beef, pork and other food products.

“Small towns can’t afford to lose a business. As a matter of fact, no towns can these days,” said Bob Golden, one of the residents waiting for news at the church Friday evening.