Police located and arrested a key suspect in the Erawan shrine bombing after mobilising technical help in one of the biggest phone data investigations in police history.
Police experts worked with the National Broadcasting and Telecommunication Commission to sort through tens of thousands of phone signals emitted near the shrine between 4.50pm and 7.30pm on Aug 17.
Police zeroed in on phone activity after they saw a suspected bomber wearing a yellow T-shirt in CCTV footage using his mobile phone after depositing a backpack at the Erawan shrine minutes before the bombing.
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Police studied the phone calls and eventually narrowed them down to three Turkish phone numbers which had activated international roaming services and were used near the blast site.
Still unidentified: Arrested on Saturday, this foreign man is under military-directed interrogation.
One of the numbers was used by a man, identified by a military source as Adem Karadag, 28, a Turkish passport holder, who rented rooms at the Pool Anant apartment building in the Nong Chok district of Bangkok.
He is believed to have delivered the explosive to the bomber, said a source.
Authorities arrested the man at the apartment on Saturday.
He is now being detained at the 11th Army Circle in Bangkok, according to police spokesman Prawut Thawornsiri.
The phone data operation started with national police chief Somyot Poompanmuang ordering the investigators to work in a special task team.
The team members are mostly leading investigators from the Metropolitan Police Bureau and the Central Investigation Bureau, the Crime Suppression Division and the police's southern operations bureau.
Also checked were calls made along the route which the suspect in the yellow T-shirt took to the shrine.
Initially, the experts reduced the number of calls to 60. And after analysing where the calls were placed and where they were going, the team focused on the three Turkish numbers.
The team found one number was actively used in Thailand and belonged to the Pool Anant apartment suspect.
The owner of another one of the three numbers had called the taxi driver who drove the yellow T-shirt bomber from Sala Daeng to Hua Lamphong train station after the blast, a police source said.
