Families in about 20 homes had to be evacuated after a large fire engulfed a mountain in Snowdonia.
About 30 firefighters were tackling the blaze at Blaenau Ffestiniog, Gwynedd, at its overnight peak.
Eyewitness Chris McPhail said: "As I was driving up I could just see the glow and a load of smoke. It just looked like a volcano."
The alarm was raised just before 20:30 BST on Monday, with residents asked to leave in the early hours of Tuesday.
North Wales Fire and Rescue Service said it was still dealing with hotspots flaring up in the area and crews remain at the scene - but say there is no immediate danger to residents.
Most residents have returned to their homes but locals are offering their spare rooms to any families still displaced by the fire.
Part of the A470 - the main route between north and south Wales - through the town was shut for several hours at Church Street but has now reopened.
BBC Wales' Laura Raymond said she was woken by firefighters "smashing open" fire hydrants at about 03:00.
"The hill was literally glowing from behind," she said.
The blaze is thought to have started behind quarry workings in an area overlooking the town called Garreg Ddu - Black Rock.
"Black Rock is like a huge gigantic lump of coal, with burning embers," said Ms Raymond.
But investigators will only start looking into what caused the fire when it is completely out.
Well done and thank you to the firefighters who have worked overnight to tackled the massive fire, our thoughts are with everyone in Blaenau Ffestiniog at this time.— Mynydd Llechi / Slate Mountain (@Slate_Mountain) April 23, 2019
Thank you also to the members of staff who stayed on site to monitor the situation over night. pic.twitter.com/CGWWYWxGBF
"We've been well looked after and the crews have done an amazing job. We're just so thankful because the crews have directed it away from the houses."
Geraint Hughes, who is managing the fire operation on the ground, said his teams had faced substantial challenges tackling the blaze.
"The rugged terrain and the steepness of it makes it difficult to put staff and personnel on the mountain to tackle it with beaters or hose-reels," he said.
He said fire crews were "currently managing" the situation, however some areas were continuing to flare-up.
Many of the evacuated residents spent the night in a cafe, including Jackie Brunger.
She told BBC Radio Wales' Good Morning Wales she was unaware of the blaze until fire crews arrived.
"It was just glowing orange and it was absolutely frightening - I've never seen anything like it," she said.
"We were told to get away as soon as we could, so we took our car and went to the cafe.
"There was ash and bits of flame coming down. How far it has spread, so quickly - it was frightening."
Sue Roberts opened up De Niros cafe for those told to leave their homes, and helped keep fire crews and police teams fed during the night.
"It's been a bit busy," she joked. "It looked quite spectacular when you think about it."