The incident caused a three-hour flight delay on flight CZ3539, which had been scheduled to depart for Shanghai Hongqiao International Airport at around noon.

China Southern Airlines said on Chinese microblogging site Weibo that a passenger’s cabin bag had emitted smoke and fire during the boarding process.

However, the fire was quickly extinguished by airport firefighters and security officers, it said.

Preliminary investigations revealed that the fire was caused by a portable charger, which was not in use at the time.

The owner of the cabin bag is currently assisting in investigations.

In a video that has been making rounds online, a flight attendant and a passenger are seen trying to douse the flames using bottles of water and juice.

Portable chargers and lithium-ion batteries – used in many consumer devices from laptops to toys – typically have to be hand carried on flights and cannot be checked in. There are also restrictions on the watt-hour (Wh) ratings of these items.