Victorian jail escapee arrested by police in Adelaide

South Australian police have arrested Victorian juvenile jail escapee Lachlan Mitchell and his accomplice after almost four days on the run.

Mitchell, a 20-year-old who allegedly fled the Malmsbury Youth Justice Centre on Tuesday in a waiting ute, was arrested without incident at a Hackham West home about 12.30am this morning, police say.

A 25-year-old Victorian man - who allegedly helped Mitchell - was also arrested and both were refused bail ahead of a scheduled appearance in the Adelaide Magistrates' Court on Monday.

Victoria Police officers will fly to Adelaide and apply to have Mitchell extradited to Melbourne.

The vehicle Mitchell allegedly escaped in is believed to have been involved in a violent carjacking on Thursday, where two men held up a driver at gunpoint in Mount Gambier.

Police continue to investigate.