Lima, Peru (CNN) -- Investigators are working to determine what caused a helicopter crash in central Peru that killed seven people, including five Americans.
The team was supporting oil exploration operations near Pucallpa, Peru, when the helicopter they were traveling in crashed Monday afternoon, according to Columbia Helicopters, the Portland, Oregon-based company that employed the victims.
Minutes after the helicopter took off from the Pucallpa Airport, authorities lost communication with the pilot, and people in the control tower could see a heavy smoke column in the distance.
A company official said Tuesday that it was unclear what caused the crash.
"We've notified all the authorities and are cooperating with everyone fully, and we'll do everything we can to learn any causes ... of the accident," said Michael Fahey, Columbia Helicopters president and CEO.
"It's a very sad day for us. We operate globally, but we're a family and we're very close to our employees. And I personally knew many of the individuals who died as our other employees know many of them," Fahey told reporters in Oregon. "We're grieving for them."
Columbia Helicopters has dispatched an investigation team to work with Peruvian authorities, Fahey said.
The victims were the aircraft's pilots and crew. No other passengers were on board, Columbia Helicopters said.
The two Peruvians killed in the crash were Igor Castillo and Luis Ramos. The Americans were identified as Dann Immel, Edwin Cordova, Jaime Pickett, Darrel Birkes and Leon Bradford.
A local police chief said three of the bodies were found away from the site of helicopter's crash and explosion, and those bodies had no burn injuries, leading authorities to believe the three passengers jumped out before the crash.
CNN's Jackie Castillo contributed to this report.