FREDERICTON -- Officials at Canada's second-largest military base say forecasted heavy rain is welcome news as crews continue to battle three fires -- efforts hampered by unexploded ammunition.

The fires have been burning for weeks at New Brunswick's Gagetown base in an area rife with the remnants of decades of soldier training.

Stephanie Duchesne, a spokeswoman for the 5th Canadian Division support base, welcomed Tuesday an Environment Canada-issued special weather statement.

It predicts more than 100 millimetres of rain in parts of the province between Wednesday and Thursday.

Meanwhile, firefighters were also battling an out-of-control, 180-hectare forest fire near Sheffield, N.B., east of Fredericton, on Tuesday.

The province says that fire started near the Portobello Creek National Wildlife Area Monday afternoon.

"The Department of Energy and Resource Development will access the fire this morning by boat to better assess the situation and see what resources are needed," spokesperson Jean Bertin said in an email Tuesday. "The cause is under investigation at the present time."

Bertin said there was no danger to any structures or people, but the fire would be monitored by air throughout the day Tuesday.

At the Gagetown base, Duchesne has said the unsafe terrain was limiting crews' capacity to put out the flames. She said "those fires were started by military training and are burning in those impact areas where military munitions are being fired into."

"When the munitions hit the ground, they are supposed to explode and if they don't they stay there on the ground and it's a hazard," Duchesne said Monday.

"Because there is unexploded ordnance in those impact areas, it limits our ability to go on foot or mechanically inside those areas."

With the area off-limits, Duchesne said firefighters were tackling the fires from the periphery, creating fire breaks using bulldozers and bringing in two civilian water bombers from Quebec.

Two of the fires were about 500 hectares each, or five square kilometres, while a third was about 26 hectares -- a small fraction of the 1,100-square-kilometre army training area, the second largest in Canada after CFB Suffield in southeast Alberta.

The fire was located a minimum of three kilometres away from the base's boundary, said Duchesne, who added there was no risk of the fires spreading beyond the training area.

(CKHJ, The Canadian Press)