An alleged terrorism suspect escaped Wednesday from the Singaporean prison where he had been detained, after being granted permission to go to the bathroom, the Home Affairs Minister Wong Kan Seng said.

Mas Selamat Kastari, who could be the commander of the Jemaah Islamiyah terror group’s Singapore arm, was allegedly involved in plotting to hijack a plane and crash it into Singapore’s Changi airport, according to the Associated Press.

Singaporean police, who are known to have a very efficient and rigorous anti-terrorism system, could not account for the escape. A massive manhunt has been launched in Singapore. Security forces are searching air, sea and land checkpoints.

“Extensive police resources have been deployed to track him down,” the home ministry said.

Seven years ago he was allegedly involved in plans to attack Singapore targets including the U.S. Embassy, the American Club and government buildings. Kastari supposedly would go to Indonesia. He walks with a limp and he is not armed.

Kastari escaped Wednesday afternoon from the Whitley Road Detention Centre. After 24 hours he is still at large.

“This should never have happened. I am sorry that it happened. An independent investigation is under way and we should not speculate on what and how it happened,” Wong said.

Mas Selamat left Singapore in 2001, after almost 40 Jemaah Islamiyah members had been arrested. In February 2003, he was detained by the Indonesian authorities for possession of falsified identification documents, and deported in Singapore in February 2006. Mas Selamat Kastari has been detained under Singapore’s Internal Security Act, according to which a person can be jailed for a long period without trial.

Singapore, which is a close ally of the United States, was named an al-Qaeda target during alleged al-Qaeda operative Khalid Sheikh Mohamed’s tribunal at Guantanamo Bay, last year.