The plane disappeared from radar screens late Tuesday, but the debris was not found until Wednesday, Xinhua reported.
There were no survivors, officials said.
The single-engine Embraer 821-Caraja plane took off from Belem, capital of Para state, and crashed near Almeirim town, 20 km from Belem's Monte Dourado airport.
The names of the victims were not disclosed.
The plane, which belonged to air charter company Fretax, was transporting nine employees of engineering company Cesbe to the Santo Antonio do Jari hydroelectric power plant, which is being built in neighbouring Amapa state.
The cause of the accident was not known and will be investigated by aviation authorities.
Fretax said the pilot had been in good health and the plane's inspections were up to date.
Both Fretax and Cesbe released statements regretting the incident and said they were providing assistance to the victims' families.