Libya’s oil production fell by 30 percent to the lowest level since September as the OPEC producer’s biggest field stopped pumping just one week after reopening from an earlier halt.

The North African nation’s output dropped to 490,000 barrels a day from 703,000 a day after the Sharara field shut, a person familiar with the situation said, asking not to be identified because of a lack of authorization to speak to media. Sharara pumped about 213,000 barrels a day before halting on April 9, the person said. The country is currently producing at its lowest level in more than six months, data compiled by Bloomberg show.

The pipeline that transports crude from Sharara in western Libya to the Zawiya refinery also stopped operating on April 9. The National Oil Corp. declared force majeure the same day on loadings of Sharara crude from the Zawiya terminal, according to a copy of the NOC’s decree obtained by Bloomberg.

Fighting among rival armed groups early last month led two of the nation’s biggest oil-exporting terminals to close, forcing a number of other fields to stop pumping. The ports have since reopened. Libya, with the continent’s largest crude reserves, pumped as much as 1.6 million barrels a day before an uprising in 2011 led to a collapse in central authority and a plunge in oil production. The country is now one of the smallest producers of the Organization of Petroleum Exporting Countries.

The NOC previously declared force majeure on loadings of Sharara crude from Zawiya on March 28, after an earlier halt at the field. The company lifted force majeure on April 3. Force majeure is a legal status protecting a party from liability if it can’t fulfill a contract for reasons beyond its control.

Zawiya, Libya’s second-largest oil terminal, was scheduled in May to ship eight Sharara crude cargoes totaling 4.83 million barrels, according to a copy of a monthly loading program obtained by Bloomberg. The outlook for the planned shipments—seven cargoes of 600,000 barrels each and an eighth of 630,000 barrels—wasn’t immediately clear.

Sharara is operated by a joint venture between the NOC and Repsol SA, Total SA, OMV AG and Statoil ASA. The field, with a total capacity of 330,000 barrels a day, resumed.