The four Indonesians deported from Singapore on Sunday are being interrogated in Jakarta to establish their links to the Islamic State in Iraq and Syria (ISIS) terror group.
Indonesian National Police spokesman, Brigadier-General Agus Rianto, said yesterday that officers from the elite Detachment 88 (Densus 88) counter-terrorism unit are handling the investigations.
"Densus 88 investigators are questioning them over their activities to determine if they have broken Indonesian laws," Gen Agus said. "We want to know if they were indeed heading to Syria to join ISIS."
He said the police will have to release them if they cannot prove links to terror activities. Police do not have powers to detain terror suspects indefinitely.
The four suspects, including a 15- year-old, were stopped by the Singapore authorities at Woodlands Checkpoint on their way into Singapore on Sunday. They were handed to Indonesian police on Batam shortly after.
Indonesian police said the men had taken the ferry from Batam to Singapore several days earlier before heading to Johor, where they spent only three hours before returning to the Republic.
Singapore's Ministry of Home Affairs yesterday confirmed that the suspects "were deported to Indonesia after investigations revealed that they had plans to make their way to Syria to fight for ISIS".
"Singapore authorities informed their Indonesian counterparts before the deportation," added a ministry spokesman.
The suspects were identified by police as Muhammad Mufid Murtadho, Untung Sugema Mardjuk, Mukhlis Koifur Rofiq and Risno.
Indonesian National Police chief Badrodin Haiti said on Monday that they were linked to radical ideologue Aman Abdurrahman, who is suspected to have orchestrated the Jan 14 attack in Jakarta from prison.
Gen Agus yesterday expressed his appreciation for Singapore's assistance. "We want to thank our Singapore counterparts for giving us complete information on the suspects and returning them to us," he said.
"We also appreciate their help in monitoring the movements of suspicious characters, although the suspects' alleged crimes have yet to be proven."