Summary：The subway system in the Azerbaijani capital of Baku will be closed on Wednesday following a massive blackout ca

 The subway system in the Azerbaijani capital of Baku will be closed on Wednesday following a massive blackout caused by a major power plant accident, Baku Metro said.

The country's busiest transport system will work in a "test mode" and will be closed to the public for the whole day Wednesday while the electricity supply is being restored, it said.

The Baku Transport Agency said that it is doing everything to reduce the increased traffic pressure.

The blackout hit most of Azerbaijan on Monday overnight due to an accident at the country's largest hydropower plant in Mingachevir. The power outage plunged Baku and nearly 40 other cities and regions into darkness.

On Tuesday, although the power supply had been gradually restored across Azerbaijan, electricity went out again in much of Baku in the evening, stranding thousands of passengers aboard subway trains.

Azerbaijani authorities said that a transformer in Mingachevir broke down, sparking a fire, which was put out quickly without causing any casualties.

The accident was largely blamed on the extreme hot weather, which has led to the widespread use of air conditioners and in turn put additional pressure on the power supply system.