LEAVING NO STONE UNTURNED: SAF personnel combing the stream leading to the Mandai West Camp yesterday. -- ST PHOTO: LIM CHIN PING

The police said yesterday that 40 foreign nationals had been arrested since Mas Selamat escaped from a detention centre on Feb 27, triggering the biggest manhunt in Singapore's history.

Officers declined to reveal where the immigration offenders had been found or what they had been doing. However, over the past 12 days, the police, Special Operations Command officers and Gurkhas have been scouring jungles across the island.

Officials believe that Mas Selamat, who has family and friends in Indonesia, is still here.

During an update on the hunt for the Jemaah Islamiah terrorist yesterday, director of operations Wong Hong Kuan said that the police were continuing to focus on forested areas.

The police had found an abandoned backpack and food, both of which they considered possible leads, said Assistant Commissioner Wong. But he did not go into specifics.

VIDEO 40 people nabbed with stringent Mas Selamat checks (2:35)

He also said that 'urban environments' would not be neglected in the search.

The police have received over 1,100 e-mail and telephone tips from the public about Mas Selamat.

Not all of those leads, however, appear to be genuine. A man was charged in court yesterday with calling in three phoney tips, including two in which he allegedly told officers that he had spotted Mas Selamat on a public bus.

AC Wong said that the police treated cases such as that one 'seriously'.

'Such deliberate misinformation distracts police resources and compromises ongoing search efforts to capture the fugitive,' he said.

Meanwhile, some people have offered police suggestions on how searches could be improved.

'We always consider all suggestions seriously,' said AC Wong. 'Of course, we use our professional judgment to prioritise search areas.'

Members of the public, especially people living or working near coastal or forested areas, have also been advised to be more vigilant and to call the police if anything suspicious is spotted, no matter how trivial.

AC Wong also said that the police were confident that Mas Selamat was still in Singapore, based on what the authorities had observed thus far.

'We know that he doesn't even have access to things that he would need to get out of the country quickly like cars, money, passports and things like that,' he said.

He also said that there had been no information regarding sightings of Mas Selamat outside of Singapore.

diothman@sph.com.sg