Residents and visitors in a small coastal city in Oregon were evacuated Sunday when a fire erupted at a seafood production plant and it was feared ammonia tanks could rupture and send dangerous amounts of the chemical into the air.

The fire at Pacific Seafood closed off the popular Bayport section of Newport. Firefighters swarmed the plant and were able to keep flames from the tanks, but continued to battle the fire Sunday evening.

The City of Newport initially issued an evacuation order for a 1-mile radius around the plant due to concerns that smoke from the fire contained ammonia. Officials later decreased the evacuation zone to a couple of blocks surrounding the plant after they determined the ammonia tanks were stable.

The city, located about 132 miles southwest of Portland, Ore., has a population of about 10,000 people. Its bayfront is a popular tourist attraction featuring restaurants, shops and tours.

Ammonia is a colorless gas with a sharp odor. High levels of exposure can cause skin, eye and throat irritation, according to the Centers for Disease Control and Prevention.

John Fuller, the public information officer for the city, told the Associated Press it is not clear what caused the fire.

Approximately 30 to 40 people were in the building when the fire broke out, Fuller said in a Sunday afternoon news conference. One firefighter was taken to the hospital for exhaustion, Fire Chief Rob Murphy said, but no other injuries were reported.

Pacific Seafood is a wholesaler and manufacturer that handles fishing, processing and the distribution of seafood across the country. One of its processing plants sits along the city’s Yaquina Bay, near a dock where sea lions gather.

Ashton Meier, Pacific Seafood’s vice president of resource sales and processing, said the company expects a major loss.

“We are incredibly thankful and glad to report that all of our team members on site are safe and accounted for and that at this time we are not aware of any injuries to others in the area,” Meier said in a Sunday evening statement.

Fuller said the initial 1-mile radius included businesses as well as residences and made up a “pretty good chunk” of the small town. A shelter originally set up at the Sam Case Elementary School was moved further north away from the plant to the Atonement Lutheran Church as a precaution.

Shelly Heim was at her home in Newport when she heard sirens and saw smoke coming from the nearby seafood plant. Flames were shooting from the roof, she said. She and her husband didn’t smell anything off in the air and didn't evacuate, but were monitoring the wind to make sure it didn't change direction and blow the smoke toward them.

“It’s heartbreaking,” the 59-year-old real estate agent said, adding that Newport has a strong working port and fishing community and that Pacific Seafood serves as a big place of employment. “It’s a big asset. Hopefully they can rebuild.”