Officers arrested the man on Monday in Kwun Tong, in connection with a telephone call or message under the Summary Offences Ordinance.

The man was believed to have posted an online audio message last month, claiming that some security guards and concierge staff at Elements, the popular Kowloon shopping centre where he works, suffered fever and were on sick leave, one police source said.

The message said some security workers at Austin MTR station and nearby luxury residential blocks such as The Cullinan, Sorrento and the Grand Austin had also fallen ill, asking the public to stay away from the area and to pass the message to others.

It added that some of them were probably infected by people who entered the city via the nearby West Kowloon high-speed railway station.

Police said officers began investigating after noticing the circulation of claims that staff at the mall were suspected to have been infected.

“The man was suspected of using a mobile phone to spread false information,” a police spokesman said.

The suspect was released on bail, pending further investigation.

Under the Summary Offences Ordinance any person who sends a message which they know to be false, for the purpose of causing annoyance, inconvenience or needless anxiety to anyone else, faces a maximum penalty of two months in jail and a HK$1,000 fine.

The ordinance dates back to 1935, and has not been amended since 1991.

The force appealed to the public not to spread false information, saying that “such attempts to cause unnecessary anxiety to others is illegal and will also bring more trouble and chaos to the community”.

The source said it was the first time the force had used the ordinance to arrest anyone in connection with smartphone-related crime, after a recent top-court ruling took away their usual way of dealing with the offences.

In April last year, the Court of Final Appeal unanimously dismissed the justice secretary’s appeal, upholding a lower court’s decision and finding that the charge of “obtaining access to a computer for criminal or dishonest gain” should not apply to a person’s own phone or computer.

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The ruling arose from the prosecution of four primary schoolteachers charged with the offence after they were accused of leaking entrance exam questions using their phones.

Prosecutors had previously relied on that charge, under Section 161 of the Crimes Ordinance, to take down offenders who took upskirt pictures on mobile phones – which could be considered computers. It carries a maximum penalty of five years in jail.

The Department of Justice has been searching for an alternative offence following the landmark ruling, which affected not only police investigations but those by anti-corruption agents. The Law Reform Commission has been also reviewing cybercrimes-related offences.

Barrister James Tze, who defended one of the teachers all the way to the top court, said that while the authorities may be using the Summary Offences Ordinance as a substitute, a balance needed to be struck between the message’s intent and freedom of speech.

Criminal law professor Simon Young Ngai-man of the University of Hong Kong said the authorities must prove an illegal purpose under the law, including causing annoyance, inconvenience or needless anxiety.

“Yes, we have our own ‘fake news crime’, but note that it merely being fake, and knowing the news is fake, is not enough to commit the offence,” Young said.

Additional reporting by Alvin Lum