The female motorist at the centre of two security intrusions here has been charged with criminal trespass and remanded at the Institute of Mental Health (IMH) for a psychiatric assessment, said the police on Wednesday.

The 27-year-old Malaysian woman, said to have a history of mental illness, was arrested on Monday in her red Perodua hatchback after she had driven into the compound of the Ministry of Foreign Affairs (MFA).

She had apparently sneaked into Singapore at the Woodlands Checkpoint on Friday and given police the slip for three days before she was finally nabbed in the grounds of the MFA, located off Holland Road.

The case prompted Deputy Prime Minister and Minister for Home Affairs Teo Chee Hean to express his "deep dissatisfaction" to the Commissioner of the Immigration and Checkpoints Authority (ICA) and the Commissioner of Police about their response to what happened.

The woman had reportedly entered Singapore just before 2pm last Friday. Officers raised the alarm two minutes later and locked down the arrival car zone, but she was gone by then.

An islandwide advisory to police patrol cars to look out for her was issued but she was not found until Monday afternoon, when she apparently tailgated a taxi for about an hour. At about 2.30pm, she entered the MFA's front gate by tailgating an authorised vehicle. She is understood to have driven in the compound for a few minutes before MFA security officers managed to stop her car.

The woman, a teacher from Kuala Lumpur, did not respond to officers' questions when she was arrested. The Straits Times understands nothing suspicious was found on her or in the car. Her family is believed to be heading here to assist the authorities.

The ICA said 50 million vehicles crossed Woodlands checkpoint in 2012, with about 350,000 visitors using it daily. There were 26 cases of attempted immigration checkpoint evasion there in the past three years, all of which have been solved.