TUNIS, Tunisia—Libya’s Sharara oil field reopened on Aug. 22 following a three-day shutdown after a pipeline valve was closed, the National Oil Corp. (NOC) said in a statement.

The NOC said it had also lifted force majeure on loadings of Sharara crude from Zawiya oil terminal.

Sharara is Libya’s biggest field and has been pumping up to 280,000 barrels per day in recent weeks. The field has been affected by repeated shutdowns because of protests by armed groups and oil workers.

The NOC said the closure had occurred at valve 17 on the pipeline leading from Sharara to Zawiya. It did not say where the valve is.

“No group has claimed responsibility for the valve closure, and no demands were made, but NOC engineers dispatched to open the valve found a gearbox had been stolen,” the statement said.

“This gearbox was removed by criminals for one purpose only, and that is to blockade the line in future,” NOC Chairman Mustafa Sanalla was quoted as saying.

After Sharara was shut on Aug. 19, sources said an unidentified armed group was thought to be responsible.

The NOC runs Sharara in a joint venture with oil companies Repsol, Total, OMV and Statoil.