Hundreds of firefighters and mountain experts join huge new search for Jay Slater 13 days after he disappeared

An 'army of volunteers' have assembled to hunt for missing teen Jay Slater as the search for him enters its 13th day.

The apprentice bricklayer, 19, has not been heard from since he phoned his pal Lucy Law on 17 June and explained that he 'didn't know where he was' while navigating a rural mountainous region in Tenerife.

He had travelled to the island to enjoy a festival with friends and ended up travelling to an Airbnb with two men that he had met on 16 June before he vanished.

Now, search efforts have been amped up again as authorities have launched a huge new hunt for Jay involving hundreds of firefighters and mountain experts.

On Friday (28 June), the Guardia Civil issued an urgent appeal for volunteer firefighters and those with experience and knowledge of rugged terrain to help them conduct a 'busqueda masiva', meaning a massive search.

Jay Slater has been missing for 13 days (handout)

A statement from cops in Tenerife explained: "Collaboration is requested from volunteer associations, civil protection teams, firefighters and even individuals who are experts in rugged search terrain."

A spokesman earlier clarified that this was not a call for 'unexperienced' members of the public to join the hunt.

Thanks to the overwhelming response from experts who are keen to help, hundreds of people are today looking for Jay or any clues which could help piece together what has happened to him.

The search party kicked off at 9am, beginning near his last-known location in the village of Masca, with volunteers told to bring food and water with them as they will likely be in for a long day.

Teams are said to be concentrating on a steep rocky area, while ravines, trails and paths are also being explored.

Police searching for Jay Slater in Tenerife (PA)

Jay has now been missing for almost a fortnight and efforts to find him have been unsuccessful so far.

His friend Brad has since spoken out about the final conversation he had with the teenager, explaining that he could hear his pal's feet 'sliding down' a hill as they chatted.

He told This Morning that he knew Jay had gone 'off the road' as he could hear the crunch of gravel or stones under his feet, but said the pair of them were initially 'laughing' about the situation.

Brad said: "He said, 'Look where I am' and I was like, 'I’ve just come out of a festival' and he didn’t seem concerned on the phone until we knew how far away he was.

"I said [to Jay], 'Put your location on' and he said 'a 15 minute drive or a 14 hour walk, I don't know if it's accurate or not' and I said, 'If it’s only a 15 minute drive, get a taxi'."