Venezuelan state oil company Petroleos de Venezuela has halted operations at its 310,000 barrel-per-day (bpd) Cardon refinery due to problems with crude supply, four people familiar with the matter said this week.

Two of the people said the crude supply shortage arose due to problems at a pipeline supplying crude to the plant.

Cardon was the only PDVSA refinery producing gasoline in the OPEC country, which has been suffering fuel shortages over the past year due to underinvestment and mismanagement at PDVSA's 1.3 million bpd refining network, and more recently US sanctions aimed at ousting President Nicolas Maduro.

The plant over the weekend halted output at its fluid catalytic cracking (FCC) and naphtha reformer units, and later halted its distillation unit, said one of the people, who spoke on the condition of anonymity. The units had been operating since November of last year after months of extensive repairs.

Workers as of Monday were attempting to restart one of the distillation units, three of the people said.

PDVSA did not immediately reply to a request for comment.

As of last week, Cardon's FCC and reformer units had been producing around 55,000 bpd of gasoline, according to union leader Ivan Freites.

A distillation unit at the neighboring 645,000 bpd Amuay refinery had been producing some naphtha to supply Cardon, while a distillation unit at the 187,000 bpd Puerto La Cruz refinery in eastern Venezuela was producing around 15,000 bpd of diesel in addition to naphtha being sent to Cardon.