The light aircraft had departed Nelson about 9.10am and was last known to be northeast of the city.
Two rescue helicopters from Nelson and Wellington were deployed to search the area.
Stuff earlier reported the plane is a privately owned Cessna 172P with the tail number ZK-BFQ, an aircraft that can carry up to four people.
According to Flightradar24, it reached an altitude of 944m before dropping to about 550m in 90 seconds.
The search appeared to be focused in an area of the Bryant Range, on the Nelson side of the boundary between Nelson and Marlborough regions, according to flight tracker Flightradar24.
Nelson Mayor Nick Smith earlier wrote on Facebook that “Nelson is anxiously hoping and praying for the occupants of the aircraft gone missing northeast of the city”.
“We wish the emergency services every success in both finding and rescuing those on the private aircraft.”
