A search is under way for a Brazilian passenger plane with at least 150 people on board that has gone missing over the Amazon rainforest.
Air force jets started searching the densely forested region for wreckage of the Boeing 737.
Aviation authorities believe the airliner struck an executive jet, which was then able to land in Para state.
The Gol airlines flight left the Amazonian city of Manaus on Friday but failed to arrive in Brasilia.
The passenger plane been due to arrive at 1812 local time (2112 GMT), before continuing to Rio de Janeiro's Antonio Jobim International Airport.
Brazil's civil aviation authority said the plane lost contact with air traffic control at 1650 local time (1950 GMT) around the remote, jungle town of Sao Felix do Araguaia.
The air force began searching close to the plane's last known position but when night fell the search was called off, to be resumed at first light.
The mayor of a remote Amazon town in the central state of Mato Grosso told Reuters news agency he believed the airliner had crashed on a farm in the area.
The central state of Mato Grosso is covered in dense rainforest
"Hospitals in the region are ready to receive the injured," he said.
Globo news agency says the airliner collided with a smaller, Brazilian-made Legacy aircraft which suffered wing damage before landing in the Cachimbo mountain range in Para state.
The Estado news agency reported that the Legacy was piloted by a US citizen who had taken off from the Sao Jose dos Campos airport near Sao Paulo.
Ramon Bueno, an aviation official in Sao Paulo, told Estado that the mid-air collision was "inexplicable."
He said that the two planes were "very modern and have anti-collision systems, which sound an alarm to alert the plane to any obstacle".
Manaus is the capital of Amazonas state in the heart of the Amazon rainforest some 1,700m (2700 km) north-west of Rio de Janeiro.
The flight between Manaus and Rio is popular with foreign tourists but there was no immediate word on the nationalities of those aboard.
Gol, a low-cost airline, has expanded rapidly in recent years to become Brazil's number two carrier.
This is the first major crash involving Gol, which was founded in 2001.
In a statement Gol confirmed the plane involved was new, having only come into service this month.