CARACAS, Venezuela (AP) — An explosion rocked a power station in the Venezuelan capital early Monday, witnesses said, adding to the crisis created by days of nationwide power cuts.

Flames rose overnight from the electrical facility in the Baruta area of Caracas. The blast contributed to a sense of chaos among Venezuelans already struggling with an economic crisis and a bitter political standoff.

Residents in Baruta gathered on a footbridge with a clear view of charred, smoldering transformers and electrical equipment.

Opposition leader Juan Guaido said three of four electricity transformers servicing the area were knocked out and that state engineers were unable to fix them. The U.S.-backed leader of the National Assembly has blamed the blackouts that began Thursday on alleged government corruption and mismanagement.

On Monday, Winston Cabas, the head of Venezuela's electrical engineers union, said critical conductors had overheated at the hydroelectric station at the Guri Dam, the cornerstone of Venezuela's electrical grid. He disputed government allegations that the dam was the target of sabotage and blamed the problem on a lack of maintenance.

"The system is vulnerable, fragile and unstable," he said.

President Nicolas Maduro has accused Guaido and the United States of staging a "cyberattack" on Venezuela's power grid. Information Minister Jorge Rodriguez earlier described it as a cyberattack on the dam's operating system, which signals to machines whether to boost or diminish power based on capacity and demand.

The U.S. dismisses the allegation.

The nationwide power outages have intensified the misery of Venezuelans. Since water pumps began failing without power, more people have been collecting water from mountain springs, and many are scrounging for scarce cash to pay for food in the few shops that are open.

"We're desperate," said Luis Sanabria, a Caracas resident who joined dozens of other people filling up bottles from a city spring.

Long lines of cars wait at the small number of gasoline stations with electricity. Some Venezuelan hospitals are caring for their most critically ill patients with the help of generators, but many operated without power, raising concerns about vulnerable patients who rely on oxygen concentrators, dialysis machines and other equipment.