Families living above a tourist railway believe thick acrid smoke from trains is making them ill.

They claim fumes from the Welsh Highland Railway has caused "considerable concern" on Rhes Segontiwm, in Caernarfon, Gwynedd.

Nia Davies Williams said: "People are getting sick. It's terrible, I'm very worried about our health."

The railway said the war in Ukraine was making it more difficult to get cleaner coal leaving them reliant on dirtier imports.

The street lies 20ft (6m) above the railway station.

Ms Williams said: "We are so worried about this horrible, acrid smoke coming into our houses. You can see the smoke in the air in the house.

"The railway is for recreation and maybe we should put health first, and maybe they shouldn't run it if they can't solve this problem."

Bar some Christmas events, Ms Williams said the railway's season ended in October.

But residents are worried about next year.

"In June 2022 we became very concerned about the quality of the smoke and we noticed that we could taste it," Ms Williams said.

"You don't dare leave the windows open in the summer anymore, because of the smoke.

"If I have the windows open just a little bit, I rush to close them immediately when I hear the train coming."

Welsh Highland Railway, she said, needed to sort it out.

"The coal used to be fine, it was really lovely, you could see and hear the trains," Ms Williams said.

"But they started to struggle about two years ago with the supply of coal because the Welsh coal mines were closing, and that's the point I'd say it started to (be) a real problem.

"They have probably bought this coal from Brazil or Colombia and they recognise themselves that it is very dirty coal but they have no choice."

Another resident, David Keeble, said it was time the railway was “shamed into taking long-term action”.

"We are being polluted,” he said.

Getting good coal was tricky Welsh Highland Railway's boss, Paul Lewin, said.

"For over a decade we have been burning dry coal from Wales, this is the Rolls-Royce material for steam trains," he said.

"It's hard coal and it burns very hot and for a long time, and there's not a lot of smoke.

"But the challenge for us is that the Welsh government has decided to end coal production in Wales."

The railway used to be able to buy good coal from Russia, but that had stopped because of of the war in Ukraine.

Now a mix of imported coal and smokeless fuel was burned, Mr Lewin said, but combining them was challenging.

He said: "Sometimes we get things wrong. We don't want the smoke either, nor do our customers, so we try to deal with that carefully."

The railway sympathised with its neighbours, Mr Lewin said, adding that closing was not an option as the business was responsible for jobs.

Welsh Highland Railway was trying to find the best fuel, he said, but sourcing it was an industry wide problem.