The ATR-42 plane was en route between the Caribbean island of Margarita and the southern industrial city Puerto Ordaz when it came down.
"We still don't know the exact cause," local governor Francisco Rangel Gomez told state TV, adding that the pilot had radioed warning the plane was in difficulty.
A Reuters witness at a nearby Puerto Ordaz hospital said 30 survivors — and two corpses — had been brought in from the crash site where wreckage was still smoldering after the mid-morning accident, hampering rescue efforts.
Gomez put the number of survivors at least 23. He said 51 people were on the Conviasa flight, while Transport Minister Francisco Garces earlier had said 47 were on board.
ATR, which makes 40-70 seat twin-engined turboprops, is a joint venture between Airbus parent company EADS and Italian aerospace group Finmeccanica.
Officials said the plane crashed on land belonging to Sidor, which has a large mill near Ciudad Guayana, but without causing any injuries or damage to installations.
"The plane fell on a waste area where they put barrels of unused steel materials," governor Gomez said.
In the last major crash in Venezuela in 2008, a plane belonging to private local airline Santa Barbara with 46 passengers on board crashed into mountains, with no survivors.
