At least 20 people have been questioned over the disappearance of British tourist Amelia Bambridge in Cambodia, police have said.

The 21-year-old backpacker, from Worthing, in Sussex, was last seen in the early hours of Thursday at a beach party on the island of Koh Rong.

As the search entered its fifth day, Preah Sihanouk province police chief Major General Chuon Narin said at least 20 people had been questioned – but no arrests have been made.

He said: “We are questioning as many people as possible and we haven’t detained anyone,” adding that he feared Ms Bambridge may have drowned.

Reports say some of those being questioned are believed to be bar workers on the popular tourist island.

Amelia Bambridge: British backpacker missing from Cambodia resort Show all 11 1 /11 Amelia Bambridge: British backpacker missing from Cambodia resort Amelia Bambridge: British backpacker missing from Cambodia resort Officials and rescuers meet during a search operation for British backpacker Amelia Bambridge, 21, from Worthing, West Sussex, who went missing after a beach party in Cambodia on the island of Koh Rong in the early hours of 24 October 2019. Sihanoukville province authority police via AP Amelia Bambridge: British backpacker missing from Cambodia resort In this photo released by Cambodian National Police on October 27, 2019, officials and rescuers meet during a search operation for the missing British woman, Amelia Bambridge in Koh Rong island in Sihanoukville province. - Cambodia deployed soldiers, police and divers to scour an island popular with backpackers after a British tourist went missing there four days ago, an official told AFP on October 28. (Photo by Handout / cambodian national police / AFP) (Photo by HANDOUT/cambodian national police/AFP via Getty Images) HANDOUT Cambodian National Police/AFP Amelia Bambridge: British backpacker missing from Cambodia resort In this photo taken October 27, 2019, Sihanoukville Governor Kuoch Chamroeun (C) and officials look over the shore of Koh Rong island during a search and rescue operation for missing British woman Amelia Bambridge. - Cambodia deployed soldiers, police and divers to scour an island popular with backpackers after a British tourist went missing there four days ago, an official told AFP on October 28. (Photo by Marady / AFP) (Photo by MARADY/AFP via Getty Images) MARADY Marady/AFP via Getty Images Amelia Bambridge: British backpacker missing from Cambodia resort Undated family handout photo issued by the Lucie Blackman Trust (LBT) of missing British backpacker Amelia Bambridge, 21, from Worthing, West Sussex, who was last seen on the Cambodian island of Koh Rong late on Wednesday night. PA Photo. Issue date: Monday October 28, 2019. Staff at Police Beach, a private venue that stages regular events, found Ms Bambridge???s purple rucksack, containing her purse, phone and bank cards, the following morning. See PA story MISSING Cambodia. Photo credit should read: Family Handout/LBT/PA Wire NOTE TO EDITORS: This handout photo may only be used in for editorial reporting purposes for the contemporaneous illustration of events, things or the people in the image or facts mentioned in the caption. Reuse of the picture may require further permission from the copyright holder. Family Handout/LBT Family handout/Lucie Blackman Trust/PA Amelia Bambridge: British backpacker missing from Cambodia resort In this photo released by Cambodian National Police on October 27, 2019 foreign divers prepare to search for the missing British woman, Amelia Bambridge in Koh Rong island in Sihanoukville province. - Cambodia deployed soldiers, police and divers to scour an island popular with backpackers after a British tourist went missing there four days ago, an official told AFP on October 28. (Photo by Handout / cambodian national police / AFP) (Photo by HANDOUT/cambodian national police/AFP via Getty Images) HANDOUT Cambodian National Police/AFP Amelia Bambridge: British backpacker missing from Cambodia resort Undated family handout photo issued by the Lucie Blackman Trust (LBT) of missing British backpacker Amelia Bambridge, 21, from Worthing, West Sussex, who was last seen on the Cambodian island of Koh Rong late on Wednesday night. PA Photo. Issue date: Monday October 28, 2019. Staff at Police Beach, a private venue that stages regular events, found Ms Bambridge???s purple rucksack, containing her purse, phone and bank cards, the following morning. See PA story MISSING Cambodia. Photo credit should read: Family Handout/LBT/PA Wire NOTE TO EDITORS: This handout photo may only be used in for editorial reporting purposes for the contemporaneous illustration of events, things or the people in the image or facts mentioned in the caption. Reuse of the picture may require further permission from the copyright holder. Family Handout/LBT Family handout/Lucie Blackman Trust/PA Amelia Bambridge: British backpacker missing from Cambodia resort Undated handout photo issued by the Lucie Blackman Trust of Amelia Bambridge, 21, who has gone missing in Cambodia. She was last seen by friends on the island of Koh Rong on Wednesday. PA Photo. Issue date: Saturday October 26, 2019. See PA story MISSING Cambodia. Photo credit should read: Lucie Blackman Trust/PA Wire NOTE TO EDITORS: This handout photo may only be used in for editorial reporting purposes for the contemporaneous illustration of events, things or the people in the image or facts mentioned in the caption. Reuse of the picture may require further permission from the copyright holder. Lucie Blackman Trust Family handout/Lucie Blackman Trust/PA Amelia Bambridge: British backpacker missing from Cambodia resort Undated family handout photo issued by the Lucie Blackman Trust (LBT) of missing British backpacker Amelia Bambridge, 21, from Worthing, West Sussex, who was last seen on the Cambodian island of Koh Rong late on Wednesday night. PA Photo. Issue date: Monday October 28, 2019. Staff at Police Beach, a private venue that stages regular events, found Ms Bambridge???s purple rucksack, containing her purse, phone and bank cards, the following morning. See PA story MISSING Cambodia. Photo credit should read: Family Handout/LBT/PA Wire NOTE TO EDITORS: This handout photo may only be used in for editorial reporting purposes for the contemporaneous illustration of events, things or the people in the image or facts mentioned in the caption. Reuse of the picture may require further permission from the copyright holder. Family Handout/LBT Family handout/Lucie Blackman Trust/PA Amelia Bambridge: British backpacker missing from Cambodia resort Undated family handout photo issued by the Lucie Blackman Trust (LBT) of missing British backpacker Amelia Bambridge, 21, from Worthing, West Sussex, who was last seen on the Cambodian island of Koh Rong late on Wednesday night. PA Photo. Issue date: Monday October 28, 2019. Staff at Police Beach, a private venue that stages regular events, found Ms Bambridge???s purple rucksack, containing her purse, phone and bank cards, the following morning. See PA story MISSING Cambodia. Photo credit should read: Family Handout/LBT/PA Wire NOTE TO EDITORS: This handout photo may only be used in for editorial reporting purposes for the contemporaneous illustration of events, things or the people in the image or facts mentioned in the caption. Reuse of the picture may require further permission from the copyright holder. Family Handout/LBT Family handout/Lucie Blackman Trust/PA Amelia Bambridge: British backpacker missing from Cambodia resort Undated family handout photo issued by the Lucie Blackman Trust (LBT) of missing British backpacker Amelia Bambridge, 21, from Worthing, West Sussex, who was last seen on the Cambodian island of Koh Rong late on Wednesday night. PA Photo. Issue date: Monday October 28, 2019. Staff at Police Beach, a private venue that stages regular events, found Ms Bambridge???s purple rucksack, containing her purse, phone and bank cards, the following morning. See PA story MISSING Cambodia. Photo credit should read: Family Handout/LBT/PA Wire NOTE TO EDITORS: This handout photo may only be used in for editorial reporting purposes for the contemporaneous illustration of events, things or the people in the image or facts mentioned in the caption. Reuse of the picture may require further permission from the copyright holder. Family Handout/LBT Family handout/Lucie Blackman Trust/PA Amelia Bambridge: British backpacker missing from Cambodia resort Undated family handout photo issued by the Lucie Blackman Trust (LBT) of missing British backpacker Amelia Bambridge, 21, from Worthing, West Sussex, who was last seen on the Cambodian island of Koh Rong late on Wednesday night. PA Photo. Issue date: Monday October 28, 2019. Staff at Police Beach, a private venue that stages regular events, found Ms Bambridge???s purple rucksack, containing her purse, phone and bank cards, the following morning. See PA story MISSING Cambodia. Photo credit should read: Family Handout/LBT/PA Wire NOTE TO EDITORS: This handout photo may only be used in for editorial reporting purposes for the contemporaneous illustration of events, things or the people in the image or facts mentioned in the caption. Reuse of the picture may require further permission from the copyright holder. Family Handout/LBT Family handout/Lucie Blackman Trust/PA

Ms Bambridge’s bag was found with money and a mobile phone still inside on a rock near the water’s edge on Police Beach and her passport was found in the room where she was staying.

Police say the phone shows she posted photos online until 3.23am but her movements after that time are not known.

Mr Narin said the search had been expanded to cover nearby islands and farther offshore in the Gulf of Thailand on Tuesday.

About 150 people have joined the search for Ms Bambridge as divers, navy and police were drafted in.

Both local and foreign volunteers are also helping, while local fishermen and neighbouring provinces in southwestern Cambodia have been alerted, police said.

Ms Bambridge’s mother, Linda Schultes, father, Phil Bambridge, and brother, Harry Bambridge, have travelled to Cambodia to help with the search.

Her father has said he fears she has been abducted.

He told Sky News: “I think someone’s taken her. I don’t think she’s had an accident. If she’d had an accident she would have been found by now.”

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Ms Bambridge set off on her trip on 27 September, when she flew to Vietnam, her family said.

They were alerted to her disappearance after she failed to check out of the Nest Beach Club hostel.

During a phone call with her younger sister Georgie on Wednesday, Ms Bambridge said her first solo trip was “doing so much for her confidence” and she was having “the best time ever”.

Mr Narin vowed police would not stop searching for the missing backpacker until she is found.

He said: “We have decided the search mission will not be ended until we find her alive, or her body if she has died.”