Libya has shut down the El Feel oilfield, an engineer at the western field said.
No more information was immediately available. The OPEC producer had managed to restart the field this year after a pipeline had been blocked for months.
A spokesman for the state-owned National Oil Corp (NOC) could not be immediately reached for comment.
El Feel, which analysts say used to produce at least 100,000 barrels a day, is operated by a joint venture owned by NOC and Italy's Eni.
The pipeline crosses through territory west of the capital Tripoli that has been fought over by armed factions loyal respectively to Libya's two rival governments.
Libya had to shut down the field late last year when a group in Zintan opposing a self-declared government in Tripoli closed a pipeline valve, blocking El Feel and the neighbouring El Sharara oilfield. Engineers later diverted the flows to enable them to restart El Feel, while El Sharara stayed closed.
