JAKARTA (AFP) - Indonesia said on Wednesday it will deport 20 foreign teachers working at a prestigious international school over immigration violations after allegations a child was sexually abused by cleaning staff sparked an outcry.

The teachers, from the Jakarta International School, are of various nationalities, including American, Australian and British, senior immigration official Maryoto Sumadi told AFP.

"Of the 26 teachers we investigated, 20 had committed immigration violations and will be deported," he said, explaining they were doing work that differed from their official job descriptions given to authorities.

The decision follows a scandal sparked in April by the alleged sexual assault of a six-year-old boy by cleaners in toilets at the school, which is a favourite with the capital's expatriates and wealthy Indonesians.

The crisis escalated when a second child came forward claiming to have been abused, and it emerged an American teacher who used to work at the school was a suspected serial paedophile under FBI investigation.

The case sparked widespread anger among the public and soul-searching in the media about the high incidence of sexual abuse at the country's schools.

Sumadi said 11 of the teachers would be deported on Friday and the others later.

"They have misused their residence permits by declaring a profession different from the scope of their job at the school," he said.

He said the teachers being deported are nine Americans, two Australians, two Canadians, a New Zealander, a Singaporean, a Taiwanese, a Briton, a South African, an Indian and a Turk.

Of those investigated, one had been cleared of breaking immigration rules while five others were still being probed, he said.

Authorities have ordered the nursery, where the alleged abuse took place, to close and police have arrested several cleaners contracted from an outside company over the allegations.

The school has strengthened security measures and pledged to cooperate with authorities' investigations.