Over a third of Vietnam and parts of neighboring Cambodia plunged into darkness this week after a crane operator knocked a tree onto a power transmission line.

State electricity company Electricity of Vietnam (EVN) said 22 of Vietnam’s 63 provinces were left without electricity, including the southern commercial center of Ho Chi Minh City, after a crane operator took out one of the country’s main north-south power lines on Wednesday.

Millions of people were affected in Vietnam, where offices and factories across the south were forced to close and traffic lights failed, reports AFP.

Electricity supply in Phnom Penh was also affected by the 10-hour power outage until power was restored on Thursday, according to the BBC. Cambodia buys 40% of its national electricity from Vietnam.

Vietnam, which derives much of its electricity from hydropower dams, is currently in the dry season.

EVN lost $700,000 in revenue because of the incident, Vietnamese state-owned newspaper Thanh Nien reported. Officials say it was one of the worst power outages Vietnam experienced.