The cause of a fire at the Garrison District Ale House in Fredericton earlier this month may never be known unless new evidence comes to light, say fire officials.

It appears the Jan. 4 fire at the popular downtown bar and restaurant started in the back deck area, said Assistant Deputy Fire Chief Paul Fleming.

But after weeks of investigation, officials still can't conclusively determine what started it, he said.

"The problem is that the fire was so deep-seated that anything that was around it was incinerated," said Fleming.

"We have to be absolutely certain when we determine the cause of a fire. There are a lot of ramifications if we get it wrong," he said.

"But it's definitely not suspicious, it was not electrical. It was some kind of igniting object."

The fire was discovered inside a wall at about 10:15 p.m., and within minutes, the restaurant was evacuated. About 30 firefighters remained on the scene through the night.

The Garrison sustained extensive damage and is expected to be closed until late spring or early summer for renovations.