UPDATE 1-Oil collected from Brazil's northeastern coast rises to 600 tonnes

(Recasts with government statement)

RIO DE JANEIRO/SAO PAULO, Oct 21 (Reuters) - Brazil has collected more 600 tonnes of oil from its northeastern beaches since Sept. 12, the government said on Monday, more than double an estimate of oil and sand collected by state-run oil company Petrobras.

Oil has been washing up on the shores of northeastern Brazil for two months, but its origin has remained a mystery so far. More than 200 locations along the coast have been affected, threatening marine life, authorities said.

Earlier on Monday, Petrobras said it had collected 280 tonnes of oil and sand from the beaches.

Brazil's government has said the oil spill is Venezuelan in origin, but has mostly stopped short of blaming their socialist government for the incident. Venezuela has denied it is to blame.

(Reporting by Marta Nogueira in Rio de Janeiro and Eduardo Simoes in Sao Paulo Editing by Chris Reese and Sonya Hepinstall)