Brazil's state oil company is halting production at its sprawling Tupi oil field to repair the offshore find's first active well.

A spokeswoman for Petroleo Brasileiro SA says the shutdown will last at least three months and lower production by 15,000 barrels a day in oil. She spoke Monday on condition of anonymity, citing company rules.

The Tupi field was discovered in 2008 and production began there in May. It is thought to hold 5 billion to 8 billion barrels of oil, making it one of Latin America's biggest deposits.

Petrobras says it was forced to close the well due to problems with bolts in a so-called Christmas tree unit that controls the flow of oil up from the ocean floor.

It said says no leaks have been detected.