The official heading the operation to rescue 12 boys and their football coach from a cave in northern Thailand says the operation is going “better than expected” after four were safely brought to the surface.

Chiang Rai provincial acting governor Narongsak Osatanakorn made the comment at a news conference on Sunday evening after rescuers extracted four of the boys from the cave where they had been trapped for more than two weeks.

Mr Narongsak said the four were then taken to a hospital. Their condition was not immediately clear.

Thailand cave rescue
(PA Graphics)

The healthiest of the 12 trapped boys and their coach had been taken out first in an operation began at 10am (4am BST). Shortly before 8pm (2pm BST) Thai Navy Seals reported on their official Facebook page that the four had been rescued.

The boys aged 11-16 from the Wild Boars team, and their 25-year-old coach were stuck in the flooded cave at Tham Luang Nang Non in Chiang Rai province since June 23.

Thai Seals' Facebook page translation
Thai Seals posted the latest news to Facebook (Facebook/PA)

President Donald Trump tweeted that US was helping the rescue effort.

Earlier, two ambulances were seen leaving the cave mouth, sparking hope that the first of the 12 trapped young footballers and their coach had made it to the surface.

One of the foreign divers involved in the operation is a former West Midlands firefighter is involved.

West Midlands Fire and Rescue Service tweeted: “Our thoughts are with everyone involved in the Thai cave rescue of 12 boys and their adult leader.

“Former West Midlands firefighter Richard Stanton, who served in Coventry for 25 years and is a world expert in cave diving, is among those leading today’s operation.”

Mr Stanton was one of two elite British divers, along with John Volanthen, who were the first rescuers to reach the group on Monday night.

Reporters at the scene said two ambulances had driven to a nearby helipad, and a helicopter was seen taking off.

Officials had said earlier that helicopters were on standby to take anyone rescued from the cave to a hospital.

Soldiers at the cave site
Thai soldiers work with pipes that have helped to drain the caves (Sakchai Lalit/AP)

In a statement released late Sunday afternoon, Chiang Rai acting governor Narongsak Osatanakorn said divers had worked with medics to assess which of the boys should come out first.

He added: “They cannot decide how many of them will be able to come out for the first operation. Based on the complexity and difficulty of the cave environment it is unknown how long it might take and how many children would exit the cave.”

Seven British divers are among a team of 18 who are undertaking the dangerous operation to free them after their ordeal that began on June 23 before floodwaters made the cave impassible.

Thailand cave rescue teams
Thai rescue team members walk inside the cave (Royal Thai Navy via AP)

The rescue attempt began at 10am local time (4am BST) and it was expected to take at least 11 hours for the first person to be rescued.

The British Cave Rescue Council (BCRC) confirmed that seven divers from the UK with “expertise in cave diving” are assisting.

Chief of operations, Governor Narongsak Osottanakorn, said 13 foreign and five Thai divers will take part in the rescue in total.

MEDIA BRIEFING NOTE Number 10 – 8 July 2018 released to Facebook at 12.35 BST Key phase begins of the rescue…

Posted by British Cave Rescue Council – BCRC on Sunday, July 8, 2018

Two divers will accompany each boy as they are gradually extracted.

Thai army commander Major General Chalongchai Chaiyakam said it may take up to four days to free all 13, depending on conditions inside the cave system.

He said the group “will continuously come out in approximately two to four days, which all may change depending on weather and water conditions”.

Thailand cave rescue
(PA Graphics)

He said two divers will accompany each boy as they are gradually extracted.

The Thai navy Seals, who have been spearheading the rescue effort, posted a photo on their Facebook page with a vow to bring the trapped team home from a flooded cave.

Screengrab from the Thai Seals message on Facebook
(Thai Seals Facebook page/PA)

The only way to bring them out of Tham Luang Nang Non in Chiang Rai province is by navigating dark and tight passageways filled with muddy water and strong currents, as well as oxygen-depleted air.