Armed Gurkhas were an unprecedented sight at the Woodlands Checkpoint into Malaysia. Over at the Tanah Merah Ferry Terminal, there was another unusual sight: immigration officers in bullet-proof vests.

Deputy Prime Minister Wong Kan Seng told Parliament yesterday: 'Security at all our land, sea and air checkpoints have been tightened, including areas where there's a possibility that he may leave our shores not from the normal immigration clearance areas.'

More than 24 hours after he disappeared and set off a massive manhunt, the Jemaah Islamiah (JI) leader who once plotted to crash a hijacked jet into Changi Airport was still on the run last night.

The alert went out to the Indonesian and Malaysian authorities as well.

Indonesian President Susilo Bambang Yudhoyono pledged his country's fullest cooperation, while Malaysia's police chiefs said they had stepped up security, particularly in neighbouring Johor.

Mr Wong, who is also Home Affairs Minister, yesterday shed a little more light on how the JI leader escaped from Whitley Road Detention Centre, in the first reported break-out from ISD detention.

The father of five had been taken from his cell to go to the visitors area to meet his family, when he asked to use the toilet. That was when he vanished.

Mr Wong told Parliament: 'This should never have happened. I am sorry that it has. An independent investigation is underway, and we should not speculate now as to what and how it happened.'

Although there was 'no information' that the ex-JI leader had plans threatening public security, Mr Wong made it clear that all stops were being pulled out to find the man.

Morning traffic along Bukit Timah and Dunearn Road slowed to a crawl yesterday as police, joined by Singapore Armed Forces soldiers, stretched a cordon from Goldhill Avenue near Barker Road to Upper Bukit Timah Road.

They checked cars and combed schools in the area before classes began. A few parents kept their children home, but most students turned up as usual.

But as Day Two of the search wore on, police activity in the area gradually wound down. By 9pm, life was back to normal for residents as all policemen and soldiers were withdrawn from the Goldhill Estate area they had concentrated on on the first night.

Businessman Eric Wong, who lives in a condominium there, said: 'I was returning home expecting to see them there, but there was no one. I guess they have determined he is not within this area.'

The authorities declined to say more about the search, except to announce that posters are being put up to urge people to call 999 immediately if they spot him.

The posters show two photographs of Mas Selamat - one with a moustache and goatee and the other, clean-shaven. 'He walks with a limp on his left leg and is presently at large,' the poster read.

Security analysts expected Mas Selamat to make a break for Indonesia, where he had links with JI leaders such as Noordin Mohd Top, the country's most wanted militant.

He was arrested twice in Indonesia, in Bintan in 2003, and again in Malang in 2006. He was handed over to the Singapore authorities in February 2006. The next month, he was detained under the Internal Security Act.

In coffee shops, on the Internet and across the island yesterday, the question on everyone's mind was how the terrorist was able to escape.

Dr Teo Ho Pin, Law and Home Affairs Government Parliamentary Committee chairman, told The Straits Times: 'I was quite surprised to find out that someone who had been placed in a high-security facility would have been able to escape.'

Earlier in the day, he had asked Mr Wong about the escape, as well as the four-hour gap between the breakout at 4.05 pm and the first Government statement to the media after 8pm.

Mr Wong replied that the security agencies had assessed that there was 'no imminent danger to the public' and their priority was to lock down the detention centre and start looking for him.

He urged the public to call the police immediately if they noted anything suspicious.

He also warned that it is a grave offence to harbour fugitives. Those caught doing so face imprisonment for life, or up to 15 years' jail.

Read also Fugitive may link up with JI comrades, Schools beef up security at all levels, How did he manage to escape?, Massive manhunt continues

bertha@sph.com.sg