Shell spokesman Ray Fisher said operations at the Deer Park refinery continued to be stable on Friday.

Production was shut on the 70,000 bpd gasoline-producing fluidic catalytic cracking unit (FCCU) on Wednesday night because of a leak in a pipe on the unit, the sources said.

A Shell spokesman was not immediately available for comment on Friday morning.

Shell examined the pipe to determine if the pinhole leak was an isolated failure of the pipe, or evidence of general thinning of the pipe wall due to corrosion, the sources said.

A single, pinhole leak could be repaired quickly, the sources said.

FCCUs use a fine catalyst under high temperature to convert gas oil into gasoline.

The Deer Park refinery is a 50-50 venture of Shell and Petroleos Mexicanos, Mexico's national oil company.