Police in Australia are searching for four intruders who set three saltwater crocodiles loose in a school administration office.

The reptiles were captured with the help of a ranger at Taminmin College at Humpty Doo on Sunday morning.

Senior Const. David Gregory said it was not yet known where the animals came from but all were in poor condition.

"The ranger that turned up was very concerned for them — they had their mouths taped up," he said.

"They haven't seen water for a long time and are undernourished."

After they had set the crocodiles loose, the offenders then entered the building with their heads covered and ransacked the office, Gregory said.

He warned there are serious penalties for animal cruelty, with fines that would work out to close to $50,000 Cdn.

The largest of the three crocodiles was two metres.

The crocodiles are now in safe hands under ranger care.