A desperate search to find missing teen Jay Slater continues on the holiday island of Tenerife.

The 19-year-old apprentice bricklayer went missing on the Spanish island last Monday and is yet to be found despite huge search efforts.

Now we outline just some of the unanswered questions that Spanish detectives will be grappling with as the hunt for Jay, from Oswaldtwistle, Lancashire, continues.

Jay was last seen walking alone on Monday morning, June 17, as he departed an Airbnb for what is a 10-hour trek through rugged, isolated terrain towards his friends’ location in the south of the island. The final known location of his phone was at Rural de Teno Park, a mountainous nature reserve where search teams have ramped up their efforts.

But his movements after approximately 8.30am on Monday are unknown.

Jay’s mother, Debbie Duncan, has called the search for her son “an absolute living nightmare”.

The five big unanswered questions:

1. Who was the mystery person his mum said had been spotted with him?

Jay’s mum Debbie, 55, disclosed that someone claims to have spotted her son walking with two men last Monday evening.

Jay was last seen that morning asking about a bus back to the south of Tenerife, where he was holidaying with friends.

She said: “Somebody has come forward to say they saw someone who they thought was Jay walking back down the road sat on a bench.

“He was with two men looking a bit worse for wear, and they were by a church, this guy has come forward and told the police about it and they are looking into it. We don’t know if it was Jay for sure, but it’s a start.

“They said it was about 6pm which is ten hours after he was seen by the lady in the village. But if it was him what was he doing there and who are these two men?”

2. Where did he go after he was last spotted?

The last location has been traced to Rural del Teno, a mountainous area in the west of the island. The closest town is Santiago del Teide.

He had been staying on the south of the island in an apartment with friends and was attempting to make the 11-hour hike back from where he ended up after a night out back to where he was staying on foot.

Friend Lucy told the Manchester Evening News: “He’s gone on a night out, he’s gone to a friend’s house, someone that he has met on holiday.

“One of the people he has met has hired a car out of here, so he’s driven them back to his apartment and Jay has gone there not realising how far away it is. He’s ended up out in the middle of nowhere.

“Jay was obviously thinking he would be able to get home from there.”

3. Is there any reason why he could have been kidnapped?

Jay’s mum Debbie also believes that the teenager could have been “bundled off” so police could also be looking into the reasons behind this. She questioned how the apprentice bricklayer could be lost in such a busy area.

Debbie said: “But if he is lost then why hasn’t anyone seen him?

“It’s busy with hikers and holidaymakers up there so if he was lost then someone would have seen him, so that’s why I think maybe he’s been bundled off somewhere.”

Debbie flew to Tenerife on Tuesday to lead the search.

She told how twisted Brits with “northern accents” had been phoning her with hidden numbers and claiming they had her son captive and were keeping him because he owed them money.

The press and police authorities have yet been unable to verify if Jay has been held captive.

4. Why didn’t Jay wait for a bus or make other travel arrangements?

According to friend Lucy, Jay had met with other friends, one of whom drove him in his hire car to another part of the island.

The teen then missed his bus back, finding himself in the rural, mountainous area as he attempted to make the journey back on foot.

His phone died around 8.50am, with his last known location registered near a hiking trail, several hundred feet above the small village of Masca.

His friend Lucy Mae received a call from him on Monday morning, saying he was attempting a long walk back through a mountainous area after spending the night with other friends.

He told her he was thirsty and his phone battery was at 1%, which died shortly afterwards.

5. Has Jay left the country?

Authorities are yet to confirm any intelligence to suggest either way if Jay has left Tenerife entirely.

However, this is highly unlikely to be the case. The nature reserve, Rural del Teno, is remote, rural, and lacks the infrastructure for Jay to have reached an airport swiftly.

The Airbnb rental Jay stayed at before vanishing is “miles from civilisation,” according to Manchester Evening News. His mum Debbie also said she has Jay’s passport.

A Foreign, Commonwealth and Development Office spokesman said: “We are supporting the family of a British man who has been reported missing in Spain and are in contact with the local authorities,” reports TeessideLive.

Express.co.uk has approached the Foreign, Commonwealth and Development Office for comment.