Darwin police are searching for four young males 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 Constable David Gregory said it was not yet known where the animals came from but all were in a 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, Constable Gregory said.

He warned of serious penalties for animal cruelty, with fines up to $50,000.

The largest of the three crocodiles was two metres.

The crocodiles are now in safe hands under ranger care.