YEREVAN (RFE/RL) — Armenia’s National Security Service (NSS) has launched an investigation into massive power outages that left much of the country without electricity on Wednesday.

Electricity supplies to parts of Yerevan and some Armenian regions were cut off early in the afternoon after sudden fluctuations in the power distribution system reportedly caused two large power plants to halt their operations. They were restored in the following hours thanks to emergency electricity imports from neighboring Iran and Georgia.

The Armenian government discussed the disruption on Thursday at a weekly meeting in Yerevan. The NSS director, Artur Vanetsyan, told Prime Minister Nikol Pashinyan and government ministers that he has ordered his subordinates to “establish the causes of the disruption of the energy system.”

“Although there are preliminary findings, I think that we need to conduct an in-depth study, investigation and conclude whether or not there was a [malicious] intent, whether there are guilty persons or whether inactivity was displayed,” said Vanetsyan. “I will report the results [to the government.]”

Hakob Vartanyan, a deputy minister for local government and infrastructures, suggested on Wednesday that the outages may have been caused by a “technological problem” at one of the power plants or an electricity frequency fluctuation in Iran. The Armenian and Iranian power grids are connected to each other with two high-voltage transmission lines.

Vartanyan, on Friday, did not exclude that this week’s massive electricity outages in Armenia were caused by a hacker attack.

“All theories are examined,” Vartanyan,, told reporters when asked about such a possibility. He said it is now looking into detailed electricity supply data from two thermal power plants that were automatically brought to a halt for still unclear reasons.

“The analysis will show where the accident started from,” said Vartanian. “The causes of the accident will be analyzed then.”

Vartanyan insisted that the Armenian power grid is equipped with the world’s most advanced computer system designed to guard against cyber attacks. But he also said: “We have seen many cases in the world where even the most reliable things can be breached because they were created by humans and humans can disrupt them.”

Pashinyan said at the cabinet meeting that the authorities now believe the causes of the country’s worst power supply disruption since 2013 were most probably “external.” “But we need to understand [for certain] what the real cause was,” he said after Vanetsyan’s announcement.