CN spokesman Jim Feeny said 15 cars and a locomotive derailed in Wapske near the village of Plaster Rock. He said 14 of those cars and the locomotive were toward the end of the train and in the area of the fire.
Of the cars that derailed, four were carrying propane and another four were carrying crude oil, Feeny said.
It was unclear how many of the cars were actually burning because emergency personnel were keeping well back as a precaution, he said.
"I cannot confirm if those cars are actually on fire due to the caution being expressed by the emergency responders," he said in an interview, calling the fire "significant."
The train's engineer and conductor, the only people on the train, were not hurt in the derailment, he said, adding that it's unclear what caused the train to leave the tracks.
"We are deploying full emergency response ... from Moncton, Toronto and Montreal," Feeny said. "Their priority is to protect the safety of the people and the environment."
Sharon DeWitt, emergency measures co-ordinator for Plaster Rock, said homes were evacuated in the immediate area and firefighters, police and ambulances were on site.
DeWitt said a news conference would be held Wednesday morning and emergency measures officials would be making no further comment until then.
"The situation has not worsened," she said. "There's no cause for alarm."
About 50 to 60 residents within a two-kilometre radius of the fire were evacuated and an evacuation centre for them was set up in a local arena, DeWitt said, though they were staying with family and friends.
A spokeswoman for Ambulance New Brunswick said no casualties were transported from the site.
New Brunswick's Emergency Measures Organization said it was notified of the derailment around 8 p.m. Hazardous materials crews were dispatched and the site has been secured by the RCMP.
The province's Emergency Operations Centre said it was monitoring smoke from the fire, which was moving east into a largely uninhabited area, and the Health Department would issue public health advisories if necessary.
The federal Transportation Safety Board has sent a team to the site to investigate.
The regularly scheduled freight train was headed to Moncton from Central Canada when it ran into trouble about 150 kilometres northwest of Fredericton.
Rail safety has become a major issue across the country since the deadly derailment in Lac-Megantic, Que., last summer and as a growing amount of fuel oils and crude petroleum is carried by train across the country.
In 2011, around 68,000 carloads of fuel oils and crude petroleum moved along Canadian rail lines, according to Statistics Canada. In 2012, that rose to nearly 113,000. Between January and September of 2013 — the most recent data available — some 118,000 carloads had been shipped via rail.
As companies and the government are looking at transport alternatives to pipelines we asked our readers wheat thy thought. In a recent poll on Castanet we asked if people were OK with companies transporting oilsands crude by rail over 850 responded. Here is the poll:
Are you OK with companies transporting oilsands crude by rail?
I don't care: 31