NT inmates bolt, return for the high-life

Inmates at a Darwin prison allegedly escaped, obtained alcohol and possibly marijuana before returning to jail.

But the incident was not reported to the Northern Territory police for more than a week.

Guards at Darwin Correctional Centre initially became suspicious, early on Sunday morning last week, when they heard five intoxicated prisoners yelling and fighting in one of the rooms over a mobile phone.

Four of those low-security inmates had allegedly earlier climbed a perimeter fence to retrieve contraband items from someone outside, the territory's correctional services department confirmed on Tuesday.

A search of the prison's Work Release Centre later uncovered two empty bottles of alcohol, five mobile phones, phone chargers, along with a cigarette lighter, rolling papers and "a small quantity of a green leafy substance".

A correctional services spokeswoman said an internal investigation was trying to determine if that was marijuana.

Police and the department are also investigating why the incident was not reported to police until Monday afternoon.

"That's what the internal investigation is trying to assess," the spokeswoman told AAP.

All five inmates were breath tested and returned to the main prison's maximum security section after returning positive results.