UPDATE 1-Shell says Capline shut as Tenn. repairs continue

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HOUSTON, April 13 (Reuters) - Shell Oil Co said the 667-mile (1,073 kilometer), 40-inch (1.016 meter) Capline crude oil pipeline remained shut on Sunday afternoon as work continued to repair a leak in Tennessee.

Shell was unable to estimate when the pipeline, which brings crude from the Gulf of Mexico to the U.S. Midwest, would return to service, the company said in a statement.

The leak was discovered on Friday afternoon by a right-of-way technician for the pipeline, Shell said.

The Dyersburg State-Gazette newspaper reported that a small crack was found by repair crews to be the cause of the leak, according to an article posted on its website.

Shell said about 10 gallons of crude oil was released into the ground by the leak.

The Capline pipeline carries oil from offshore platforms in the Gulf to a terminal in Patoka, Illinois, about 60 miles (97 km) east of St. Louis.

Shell Oil Co is the U.S. unit of Royal Dutch Shell Plc (RDSa.L). (Reporting by Erwin Seba,editing by Leslie Gevirtz)