An explosion rocked the Petrobras operated Cidade de Sao Mateus FPSO Wednesday, killing five people and leaving four others missing.
The blast happened around noon off the coast of Espirito Santo and sparked a fire that has since been contained.
Five workers have been confirmed dead and four others are still missing, rig owner BW Offshore said.
Two crew members are in critical condition and have been taken off the vessel.
Search and rescue operations are ongoing.
There were 74 workers on board the FPSO at the time of the accident.
Production at the 2,200 barrel per day platform has been stopped and the unit has been shut down.
“The accident was controlled immediately through our emergency plan and with all necessary resources,” Brazil’s Petrobras said.
Brazil’s oil regulator ANP said there have been no reported oil spills.
The FPSO was operating at the Camarupim and Camarupim Norte fields in Espirito Santo littoral 74 miles off Brazil’s coast.
The cause of the blast has not been determined although a union official told the BBC a gas leak could be to blame.
“This is a tragic day, and our primary focus now is on the crew and their families. We cannot rest until the last four of our men are found,” BW Offshore CEO Carl Arnet said.