Azerbaijan experienced a total electrical blackout early on July 3, but authorities report that supplies are slowly being restored throughout the country.
Authorities attributed the massive outage to an explosion at a hydroelectric power station located in Mingachevir.
The office of the presidency said that extremely hot weather - which prompted widespread use of air-conditioning - caused an overload of the electrical system and led to the accident.
The outage put residents of Baku in the dark for hours. But by early morning, power had been restored in many areas and at essential facilities like hospitals, military bases, the Baku subway, and the airport, APA reported.
The government said electricity supplies to most districts of Baku, including Yasamal, Nasimi, Khatai, Binagadi, Sabayel, Khazar, and Sabunchu, as well as the nearby town of Khirdalan, had been restored.
Temperatures are expected to soar later on July 3 to a high of 43 degrees Celsius and remain in that range through July 4, forecasters say, posing further strains for the electrical system.
Azerbaijan's Ministry of Emergencies said firefighters brought the fire from the explosion in Mingachevir under control. It said no one was hurt or killed in the explosion.
"The electricity supply will be gradually restored in the country. There is no reason to panic," a ministry official said. The ministry said electricity had been restored in some northern regions of the country, too.
Yahya Babanli, a spokesman for Azerenergy, a state energy supply company, told Real TV that Azerbaijan is moving to import electricity from Georgia and Russia.
By early morning, the electrical supply had resumed in northern and western areas, including Mingachevir city, as the result of an energy exchange with Russia, Real TV, APA.az, and Azerenergy reported.
Babanli said that it could take a while for the power plant to recover from the explosion, which occurred at a substation connected to several high-voltage power lines.
"This technical process will take a while since the system has collapsed. But because of their strategic importance, Mingachevir and the western regions are supplied with electricity via our local resources," RFE/RL cited him as saying.
