Twenty SA schools evacuated after threats

Bomb threats at 20 schools in South Australia are believed to be linked to similar threats interstate.

Schools across Adelaide, Gawler, Naracoorte and Murray Bridge were evacuated on Friday after a second consecutive day of hoax calls.

Education Minister Susan Close says she understands the schools received computer-automated threats within quick succession of each other.

"They appear to have the characteristics not only of calls that have come in interstate but I think likely also overseas as well," she told reporters.

Schools had responded quickly and calmly and parents were contacted.

SA Police were working closely with the Australian Federal Police and interstate counterparts, Assistant Commissioner Scott Duval said.