Two people are feared dead following a light plane crash in Queensland's Darling Downs.

The twin turboprop Reims-Cessna F406 aircraft came down near Oakey, north-west of Toowoomba, at 3pm today.

It was heading to Brisbane from Warwick.

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It circled before crashing and is understood to have dropped from 3000 feet to 1200 feet in seconds.

Two men, the pilot and co-pilot, are both feared dead.

The Australian Transport Safety Bureau said it had started an investigation.