The death of National Parks and Wildlife Service officer John Garland, 65, on Friday has devastated his fire service colleagues, who praised his professionalism.

Mr Garland, a divisional commander and firefighter, was involved in a mopping up exercise at a bushfire site in Cessnock, when a problem tree he was assessing fell on him.

“He was trapped by the tree and, despite frantic efforts from those around him, was caught under the tree and passed away,” NPWS head Sally Barnes told reporters in Sydney.

A Westpac Rescue Helicopter had been sent to the area following the 12.30pm incident, but Mr Garland died before it could reach him.

“He was a very experienced firefighter and he was also a very experienced tree expert,” Ms Barnes said.

“He gave his life for the community of NSW, protecting life and property.”

Mr Garland was fit, well-known and much loved by his friends, family and colleagues and would be “extremely missed”.

‘’John has been in the Upper Hunter office at Scone for 11 years and worked in the timber industry before that.’’

“He leaves behind a family, a wife, children and many, many grandchildren. They were his life.”

NSW Rural Fire Service Commissioner Shane Fitzsimmons said Mr Garland’s death was a tragedy.

“This is an incredibly sad time and my thoughts and prayers are with the firefighter’s family and friends,” he said in a statement.

State Emergency Service Minister Steve Whan also expressed his condolences.

“This is a devastating time and I would like to praise the ongoing professionalism of these firefighters who work under extreme conditions,” he said.

Ms Barnes said Mr Garland was a champion of occupational health and safety and said the incident would be investigated.

“This hits very hard when one of your own is taken,” she said.

The bushfire had been burning at Baraba Lane, off Watagans National Park, since Monday.

RFS Assistant Commissioner Rob Rogers told reporters it was in remote terrain and 33 firefighters had been working on it, along with four helicopters, each day.

He said the cause of the fire, which had been contained, would be investigated.

The RFS attended more than 100 bush and grass fires last week.