The Fire Services Department said its investigators began a probe after a fire extinguisher exploded in a restaurant on Lantau in September, injuring a woman.
They found the registered contractor for the installation had issued a certificate to the restaurant in February last year that stated the extinguisher was functioning properly and met requirements laid out by the department.
Investigators said they found the fire extinguisher to have suffered severe corrosion, and suspect the contractor had not inspected the equipment in person.
Firefighters referred the case to the police for criminal investigations.
A 62-year-old man, believed to be the contractor, was arrested on Wednesday.
He has been released on bail pending further investigations.
Acting assistant divisional officer Choy Lit-pong of the Fire Services Department said officers have been conducting inspections based on certificates issued by contractors.
Choy also said authorities are not ruling out requiring contractors to provide more proof when submitting safety certificates in future.
