HOUSTON – Chevron Corp. now says it caused an oil spill off the coast of Brazil, which is likely to pose problems for the oil producer in a region crucial to its growth.

Oil has been seeping from the ocean floor since Nov. 8, near where Chevron was drilling an exploratory well. But until now, the company has been slow to acknowledge that the spill was directly related to the drilling, saying instead that the well was "suspected to be contributing" to seepage.

On...