The Gospers Mountain bushfire that spread into Lithgow and surrounding New South Wales villages on the weekend has severely damaged infrastructure at the historic Zig Zag Railway.

Key points: A historic railway in the Blue Mountains area has been damaged by the massive Gospers Mountain bushfire

A historic railway in the Blue Mountains area has been damaged by the massive Gospers Mountain bushfire While significant, a spokesperson said some of the most value parts of the site remain intact

While significant, a spokesperson said some of the most value parts of the site remain intact The fire narrowly missed a museum nearby, with the president crediting an earlier spot fire for clearing bush that would have ignited

A toilet block, office, storage containers, railway sleepers and a communications hut were lost in the blaze, a Zig Zag Railway spokesperson said.

In a statement the spokesperson said the bushfire also damaged signalling equipment and crippled power and water supplies at the site.

But the historic railway station building and the majority of rolling stock were undamaged thanks to the efforts of firefighting volunteers.

The burnt out Zig Zag Railway office contained records dating back 45 years.

"There were some very old carriages lost, but they were already damaged by vandalism, and they weren't the ones that we were actively restoring," the spokesperson said.

"The toilet block can be replaced much easier than the historic station."

The railway committee is encouraging people to stay away from the area until a proper safety assessment came be done.

Burnt tree trunks litter the entrance of a railway tunnel at the Zig Zag Railway. ( Supplied: Zig Zag Railway )

Museum escapes damage

At the nearby Lithgow State Mine Museum Heritage Park and Railway, early preparations by volunteers and assistance from fire crews meant that three historic buildings survived the worst of the fire.

"We were very lucky actually," museum president Ray Christison said.

"We had almost a little miracle happen up there."

Buildings at the Left Hand Gully at the Lithgow State Mine Museum remain untouched after a bushfire passed through the area. ( Supplied: Lithgow State Mine Museum )

Mr Christison said it was lucky that a spot fire, which sparked nearby on Friday, had burned along the ridge on the western side of the premises and cleared the undergrowth in scrubland.

"I [that] think helped us to save our buildings on Saturday," he said.

"It was God's own backburn I think."

Mr Christison said the ferocity of Saturday's fire was unlike anything he had seen before.

"It was horrendous," he said.

"I've lived in fire front areas all my life and I've never seen a fire move that fast."