By Mircely Guanipa and Deisy Buitrago

PUNTO FIJO, Venezuela (Reuters) - Venezuela's main oil export port of Jose and the country's four crude upgraders have been unable to resume operations following a massive power blackout on Monday, according to industry workers and a union leader close to the facilities.

The most recent oil shipment for export, on the carrier Dragon chartered by Russia's Rosneft, left Jose, which is owned by state-run PDVSA, on March 24, according to Refinitiv Eikon vessel-tracking data and PDVSA's trade documents.

"There is no electricity, everything is paralyzed," oil workers' union leader Jose Bodas told Reuters on Tuesday.

The blackout, Venezuela's second major power outage in a month, left streets mostly empty in the capital Caracas as school and work were canceled.

President Nicolas Maduro's government again blamed the outage on an "attack," which comes amid a power struggle with the opposition and tensions with the United States.

Local experts and electrical engineers told Reuters both the current outage and a prolonged blackout that began March 7 were due to years of underinvestment and lack of maintenance.

Several electricity transmission lines were affected this time, halting power at PDVSA's oilfields, upgraders and terminals, according to one of the sources. The total effect of the outage on the company's operations is unclear.

Neither PDVSA nor Venezuela's oil ministry immediately responded to requests for comment.

PDVSA's four crude upgraders in the country's Orinoco Belt, capable of converting up to 700,000 barrels per day (bpd) of extra heavy oil into exportable crude grades, are operated along with Chevron from the U.S., Norway's Equinor, France's Total and Rosneft.

"We tried to restart operations last night, but for now only emergency staff are working there," an upgrader worker said.

The Petropiar upgrader, part-owned by Chevron, and the Petromonagas facility, in which Rosneft has a minority stake, could not fully restart since the first blackout hit on March 7, three sources said. Petrocedeno, part-owned by Total and Equinor, and Petrosanfelix, which is fully-owned by PDVSA, halted operations after the blackout on Monday.

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Representatives for Chevron, Rosneft, Total and Equinor did not immediately respond to requests for comment.

Another source said workers would attempt to restart the upgraders overnight or on Wednesday.

The blackout earlier this month also interrupted oil exports at Jose, the lifeblood of the OPEC nation's economy, eroding total export volumes and causing delays in loading and discharging oil.

Another PDVSA worker, who spoke on the condition of anonymity because they were not authorized to speak publicly, said the port had been evacuated around 2 p.m. local time on Monday.

(Reporting by Mircely Guanipa and Marianna Parraga, writing by Luc Cohen; editing by Rosalba O'Brien, Bernadette Baum and Chris Reese)