PARIS (AFP) - Metro trains resumed operating on one of Paris's busiest lines early Wednesday (Aug 1) after a technical problem paralysed the network for hours, forcing the evacuation of hundreds of people through dark tunnels in stifling heat.

The breakdown began shortly after 8:00 pm Tuesday (2am Wednesday Singapore time) when a train on Line 1, which serves the Louvre, the Champs Elysees and other tourist landmarks of the capital, suddenly halted between stops in the popular Marais district.

Network operator RATP was unable to determine the cause of the incident, forcing the shutdown of the entire line. Passengers needed to be evacuated from at least eight trains in a more than two-hour operation that required around 40 rescue workers and 150 RATP agents to help people climb down from the cars and walk out along the tracks.

Many passengers vented their frustrations on social media, posting videos of a chaotic evacuation and complaining about a lack of information about what has happening.

"No air-conditions, a real oven," tweeted Assma Maad, a journalist at Buzzfeed France.

Five people required treatment for heat exhaustion during the evacuations, which came as France is being hit with a weeks-long heat wave.