A passenger's portable charger caught fire on Tuesday night on a bus in Yuen Long, police said, sparking a blaze that left two injured.

Police said they believe the charger – owned by a 25-year-old passenger – started smoking and ignited while the KMB bus was travelling along Yuen Long Highway toward Tin Shui Wai shortly before 8.30pm on Tuesday evening.

The man suffered burns to his left hand, and the fire spread on the upper deck.

The bus driver felt unwell from smoke inhalation, and both were taken to Pok Oi hospital for treatment.

Firefighters put out the blaze, and an initial inspection found no suspicious circumstances.