US energy giant Chevron said Monday it has suspended drilling following an oil spill in waters off Rio de Janeiro state which prompted Brazil to demand a "rigorous investigation."

Chevron Brazil said it was "responding to oil seeps and a subsequent sheen that has occurred in the vicinity of the Chevron-operated Frade project located 370 kilometers (230 miles) offshore northeast of Rio De Janeiro in water depths of approximately 1200 meters (3800 feet)."

"A precautionary suspension of development drilling activities at Frade remains in place," said the company, which estimated the volume of the sheen to be "between 400-650 barrels of oil."

Chevron said investigations were continuing to determine the cause and source of the oil seeps.

It added that 17 vessels were working on a rotational basis to deploy containment booms and undertake skimming and washing techniques aimed at controlling the sheen.

And it said inspections of the Frade facility "continues to confirm that production activities are unrelated to the seeps and sheen, and production is continuing."

Brazilian President Dilma Rousseff has demanded a "rigorous investigation into the causes of the accident."

Repsol finds more oil off Brazilian coast
Madrid (AFP) Nov 14, 2011 - Repsol, Spain's biggest oil group, said Monday it has made a new oil discovery off the coast of Brazil together with Chinese partner Sinopec, Britain's BG Group and Brazil's Petrobras.

The field containing "high quality" crude was discovered nearly 300 kilometres (185 miles) off the coast of Sao Paulo at a depth of 4,830 metres, it said in a statement.

Repsol and its partner Sinopec have a 25 percent stake in the consortium which is led by Petrobras which has 45 percent. The remaining 30 percent is held by BG Group.

In June, the company announced it had discovered two grades of "good quality" oil about 190 kilometres off the coast of Rio de Janeiro.

Last week, Repsol announced its largest-ever oil discovery, saying it had discovered nearly a billion barrels in unconventional oil and gas in Patagonia, a find that doubles its proven reserves in Argentina.

Repsol has a significant portfolio of projects in Brazil, including a producing field, a block under development, two planned pilot projects and 14 exploration blocks of great potential.