An oil tanker left Libya’s easternmost port without loading crude due to a strike by the terminal’s security guards, underscoring the fragility of the OPEC nation’s resurgent production.

The Front Cruiser is the first vessel to withdraw from the port of Hariga without taking on a cargo since the strike began last month, according to a person familiar with the situation. Another tanker, the Delta Eurydice, canceled a scheduled arrival at Hariga and diverted instead to Es Sider, the country’s largest oil port, the person said, asking not to be identified because they lack authorization to speak to media.

Members of the Petroleum Facilities Guard are striking at Hariga in a dispute over delayed salary payments. They’ve also threatened to halt cargoes at Es Sider and another eastern port, Ras Lanuf, unless they get paid this week.

Libya’s oil output rose from almost zero to nearly 1.25 million barrels daily after a blockade of ports and fields by eastern-based armed forces ended in September. A tentative peace in the North African country’s civil war led to the lifting of the blockade. However, the state energy company is struggling to maintain the recovery due to the dilapidated condition of many pipelines and other facilities, as well as strikes at ports.