The investigation continues into the murders of two British tourists on the Thai island of Koh Tao.
Police
in Thailand say they have still not formally identified any suspects in
the murder of Hannah Witheridge, 23, from Great Yarmouth, and
24-year-old David Miller from Jersey, who were found on a beach in the
early hours of Monday morning.
According to BBC reports, police are now seeking a group of men who were heard singing 'Western pop songs' near the crime scene.
Two
British men, brothers Christopher and James Ware who were friends of
the deceased, were questioned earlier but police said there was no
evidence linking them to the murder.
The two have been asked to stay in Thailand to help with the inquiry.
They were stopped at Bangkok International Airport as they prepared to leave the country.
Forensic
tests carried out on Ms Witheridge's body found traces of semen from
two different men, but neither matched DNA from the brothers or Mr
Miller.
Police said blood stains had been found on the clothes of some of the 11 Burmese migrants who were also being questioned.
Post-mortem
examinations showed Ms Witheridge died from head wounds and Mr Miller
from severe blows to the head and drowning. He also had wounds on his
hands, which suggests a struggle had taken place.
According to
the Tourism Authority of Thailand, the island has been on lockdown since
the murders were discovered, but the BBC said restrictions were not put
in place straight away and people have been allowed to leave. It also
said the crime scene wasn't sealed off immediately so evidence could
have been tampered with.
A TAT spokeswoman said: "We understand
this to be an isolated incident and is very much out of character for an
island which is much loved for its quaint atmosphere.
"Local
authorities have begun a thorough investigation and have put
restrictions in place for the time being to prevent anyone leaving the
island.
"This may have an impact on tourists' travel plans so we
suggest they contact their travel agent, tour operator or chosen hotel
for further advice if they are currently on, or are due to travel, to
the island in the next few days.'¨
"Our thoughts and condolences are with the families and friends affected by the news."
It
is believed that Hannah and David did not know each other when they
first arrived in Koh Tao separately at the end of August but could have
become friends later on.
They met while staying at the same
hotel, where they also become friends with a third British traveller,
and all three arranged to go out together on Sunday night, according to
the local officers.
The bodies of the pair were found hacked to death, hidden behind rocks, and a blood stained hoe was found nearby.
TAT
said that while Koh Tao was not on the main tourist trail, it was
popular with backpackers and those with a keen interest in snorkelling
and diving.
It added: "Koh Tao, and other beach and island destinations across Thailand, remain safe for tourists to travel to.
Hannah's
father, Tony Witheridge, runs Carefree Holidays, which runs
self-catering parks in Hemsby, Newport and Winterton on Sea near Great
Yarmouth and the Norfolk Broads.