A Brazilian federal prosecutor filed criminal charges against U.S. oil company Chevron and drill-rig operator Transocean for a November oil spill off the coast of Rio de Janeiro, the prosecutor's office said on Wednesday.

The prosecutor, Eduardo Santos de Oliveira, also filed criminal charges against key executives and employees at Chevron and Transocean , owner of the world's largest oil rig fleet. Among the defendants is George Buck, 46, a U.S. national in charge of Chevron's operations in Brazil, the office said in a statement.

The charges allege that the spill created a prolonged contamination time bomb that threatens the entire marine ecosystem.

In addition to Buck, prosecutors levelled criminal charges against five other Americans, five Brazilians, two Frenchmen, two Australians, a Canadian and a Briton.

All were ordered to turn in their passports on Saturday and remain in the country, pending charges. Each individual will be required to post 1 million reais (346,871.85 pounds) bail and each company 10 million reais to ensure payment of future fines, the statement said.

Prison sentences could reach as high as 31 years.

The criminal prosecution follows a 20 billion reais (6 billion pounds) civil lawsuit filed in November over the spill, the largest ecological fine in Brazilian history. The indictments stem from a 3,000-barrel oil spill in the Frade field, about 120 km (75 miles) off the coast of Brazil's Rio de Janeiro state.

The spill was less than 0.1 percent of the size of the 4-million-barrel BP oil disaster in the Gulf of Mexico in 2010.

(Editing by Dale Hudson)