Hong Kong police have arrested a school bus driver for allegedly driving under the influence of drugs after consuming marijuana, with one student on board at the time of the incident.

Police on Tuesday said they had arrested the 23-year-old, surnamed Yau, after officers noticed the vehicle being driven erratically near the junction of Prince Edward Road East and Concorde Road in Kai Tak.

Following a preliminary investigation, the driver failed a rapid oral saliva test and was subsequently arrested on suspicion of driving under the influence of drugs.

A source said officers became suspicious after the school bus appeared to swerve while the suspect was behind the wheel.

Officers stopped the vehicle and administered the rapid oral saliva test, which came back positive, the insider added.

The man was arrested and taken to Ngau Tau Kok Police Station as part of the investigation. The case has been referred to the Kowloon East traffic unit.

Additional reporting by Danny Mok.