A video posted online showing a naked couple having sex in broad daylight on the balcony of a flat in a high-rise building at Hong Kong's former Kai Tak Airport led to the arrest of a woman, police said on Wednesday.
As of Wednesday morning, a citywide police search for her male partner was still under way.
The 36-year-old woman was arrested by officers from the Sau Mau Ping criminal investigation unit outside a Muk Tai Street residential building near Kai Tak MTR station on Tuesday, according to the force.
She was detained on suspicion of outraging public decency under the common law - an offence that is punishable by up to seven years in jail.
Barrister Albert Luk Wai-hung said the offence of indecency in public under the Crimes Ordinance was more appropriate for this case than the offence of outraging public decency.
Under the ordinance, a person who, without lawful authority or excuse, in any public place or in view of the public indecently exposes any part of his or her body shall be guilty of this offence punishable by up to six months in jail and a HK$1,000 (S$175) fine.
"The balcony is described as a private area, but having sex and exposing their bodies indecently there is obviously visible by the public. Their act is in breach of the law," Luk said.
Those who posted the video online could also face prosecution for publishing obscene articles under the Control of Obscene and Indecent Articles Ordinance - an offence that carries a maximum penalty of three years in jail and a HK$1 million fine, he said.
"An active investigation is still under way. Further arrests are possible," police said on Wednesday.
The woman has been released on bail. She is required to report to police next month.
According to the force, officers began investigating the case after discovering a video posted online recently showing a man and a woman engaging in indecent behaviour on the balcony of a flat in a Muk Tai Street building.
After gathering evidence, the arrest was made outside the block of flats on Tuesday.
The 16-second clip, seemingly filmed from a nearby building, shows the naked couple having sex on a balcony.
As the suspect has remained tight-lipped, crime-squad officers are still investigating when the incident happened.
Police said the investigation was ongoing.