A renewed search for missing Lancashire teenager Jay Slater is under way in Tenerife after Spanish police appealed for expert volunteers to help.

The 19-year-old, from Oswaldtwistle disappeared following an attempt to walk back to his accommodation on June 17.

On Friday, the Guardia Civil appealed for volunteer associations, such as firefighters, and individual volunteers who were experts in rugged terrain to assist in a “busqueda masiva”, or massive search, on Saturday.

The search in the village of Masca, near to his last-known location, is being co-ordinated to take in a steep rocky area, including ravines, trails and paths.

It marks the 13th day in the search for the apprentice bricklayer.

An appeal poster for Jay Slater, 19, who went missing during a holiday in Tenerife  (Image: Family Handout/PA)

Mr Slater attended the NRG music festival on the island with two friends before his disappearance and his last known location was the Rural de Teno Park in the north of the island – which was about an 11-hour walk from his accommodation.

He had reportedly been driven to an Airbnb property in Masca.

According to reports, media were told in a press conference on Saturday that two men who were reported to have rented the Airbnb are “not relevant” to the case.

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On Friday, Mr Slater’s friend Brad Hargreaves told ITV’s This Morning he had been on a video call with him before his disappearance when he heard him go off the road.

He said: “He was on the phone walking down a road and he’d gone over a little bit – not a big drop – but a tiny little drop and he was going down, and he said ‘I’ll ring ya back, I’ll ring ya back’ because I think someone else was ringing him.”

The Airbnb Casa Abuela Tina in Masca, Tenerife, where missing British teenager Jay Slater resided prior to his disappearance (Image: James Manning/PA)

He confirmed he could see his friend’s feet “sliding” down the hill and could hear he was walking on gravel.

But, Mr Hargreaves said he and his friend were both laughing at that point.

He added: “He didn’t seem concerned on the phone until we knew how far away he was.”

He told the programme he still had hope for Mr Slater and was “praying” for him to come home.

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Earlier this week, his mother Debbie Duncan, who travelled to the island following his disappearance, said money raised online would be used to support mountain rescue teams, and to cover her own accommodation and food costs.

Donations flooded in after GoFundMe appeal “Get Jay Slater home” was set up by Lucy Law, his friend and the last person to speak to him, and by Friday more than £40,000 had been raised.

Members of a search and rescue team near the last known location of Jay Slater (Image: James Manning/PA)

In an update on Thursday, Ms Duncan said: “We are currently working with GoFundMe to withdraw part of the funds, which are being safely held.

“I wanted to share that these funds will be used to support the mountain rescue teams who are tirelessly searching for Jay.

“Additionally, since our stay in Tenerife needs to be extended, we will also use the funds to cover accommodation and food expenses.”

Ms Law said Mr Slater told her in a frantic phone call before he went missing that he was “lost in the mountains, he wasn’t aware of his surroundings, he desperately needed a drink and his phone was on one per cent”.

Search teams, co-ordinated by the Guardia Civil, have since mounted a huge manhunt using helicopters, drones and search dogs to scour mountainous areas of the island, but are yet to find the teenager.

Ms Duncan has described her son’s disappearance and the wait for news as a “living nightmare”.