Australian Transport Safety Bureau investigators have launched a probe into an incident in which a passenger jet made a precautionary landing at Mackay Airport on Monday evening.

Passengers begin to emerge from the aircraft after it made a safe touch down at Mackay Airport.

The Jetstar 717 aircraft – carrying 50 passengers and a crew of six -- was on descent to Hamilton Island, about 20 nautical miles south of Mackay.

A Jetstar spokesman said the crew detected an acrid smell in the cabin. The pilot elected to divert the aircraft to Mackay.

The aircraft made a safe landing at 5.12 p.m.

No-one was injured and investigations are continuing.