"He came out through the bathroom window..."

Wong said that the investigation into Kastari's escape concluded that he received no help from the centre's guards or staff and was not assisted by someone from the outside.

The escape was seen by some experts as highly embarrassing for Singapore, which prides itself on tight security. Wong said the authorities were considering building a new detention centre inside a prison.

Singapore, a strong U.S. ally and a major base for Western businesses, sees itself as a prime target in the region after it said it foiled JI plots in 2001 to attack its airport and other sites, including the U.S. embassy and the American Club.

(Editing by Neil Chatterjee and Alex Richardson)