Because of a lack of fuel at Cruzeiro do Sul, the Constellation had been on the ground for 4 days. Several hours after the arrival of to fuel trucks from Porto Velho the Connie was refueled directly from the trucks. The aircraft took off and climbed to FL80. Suddenly the no. 3 engine failed, followed 10 minutes later by another engine. Cargo was jettisoned, but the aircraft continued to lose altitude. A forced landing was attempted on the Cruzeiro-do-Sul – Tarauac  highway, but the aircraft struck some trees and crashed in flames. Another aircraft had been refueled just after PP-PDG and had to reject the takeoff because of an engine failure. PROBABLE CAUSE: Refueling directly from the trucks, without allowing sufficient time for the fuel to settle.