A group of New World First Bus drivers was on Monday planning to stage a work-to-rule campaign in protest of the arrest of one of their colleagues during the anti-government protests the day before.
The 37-year-old driver was taken into custody on suspicion of dangerous driving and possessing an offensive weapon.
Police said he was behind the wheel of a number 970 bus that was travelling in a high speed on Nathan Road, and that he was honking in an "unreasonable" manner.
Officers also said they found a spanner in his bag after he was taken to a police station.
The driver was freed on bail on Monday.
The head of the New World First Bus Staff Union, Lam Kam-piu, told a radio programme on Monday that drivers were unhappy with their co-worker's arrest, saying they won't normally speed up if there were many people on the road.
Lam said the driver could have been honking to warn people to stay out of danger in a chaotic situation.
He also said it's common for drivers to be carrying tools such as a spanner for work purposes, including adjusting the rear-view mirror of the vehicle.
New World First Bus said it knew that some drivers carried a spanner to adjust the rear-view mirror, and the company has not banned them from carrying one.
A spokesman says it will talk to the arrested driver to learn more.
Lam urged the firm to go through the travel records of the bus, such as its 'black box', for more information such as its speed at the time.
The union was seeking the help of lawyers and district councillors in the case.
Police on Sunday arrested 289 people following a day of chaos in Mong Kok and Yau Ma Tei.
People took to the streets for an anti-government rally on what would have been the day of the Legislative Council election, with the chaos lasting for hours.
A majority of those detained were accused of illegal assembly.
Last updated: 2020-09-07 HKT 21:15