Police here have arrested 13 people linked to a video posted on YouTube showing young Iranian men and women dancing on a rooftop to Pharrell Williams' feel-good hit "Happy," local media reported Wednesday.
The arrests drew outrage on social media, where critics accused Iranian authorities of making it a crime to be happy. The hashtag #FreeHappyIranians was tweeted thousands of times.
There were unconfirmed reports late Wednesday that the detainees had been released.
The young Iranians are part of a worldwide Web movement of youths posting scenes of choreographed revelry to the tune penned by the U.S. singer and songwriter.
On his Twitter feed, Williams declared, "It's beyond sad these kids were arrested for trying to spread happiness."
The tune is not political and invites listeners to "clap along if you feel like a room without a roof." The chorus line: "Because I'm happy."
But the video of young Iranians dancing to the song was labeled "obnoxious" by the Tehran police chief, Hussian Sajedinia, who announced the arrests on State TV late Tuesday.
"In two hours, we recognized the participants in the 'Happy' video and rounded up 13 of them," Sajedinia said.
Six of those arrested -- three men and three women -- told Iranian television that they had been deceived and did not realize the clips would end up on the Internet. They said they were under the impression the scenes were part of an audition for actors and actresses.
"They had told us that this video won't be released anywhere and that is was for our own joy," one of the women was quoted as saying by the Associated Press.
The potential charges were not specified. But it seemed likely those arrested would be accused of running afoul of Islamic codes of behavior that call for modesty in attire and behavior.
Officials in the Islamic Republic are leery of western styles of dress, music and other cultural manifestations that they deem decadent.
In the video, young men and women dance and frolic together to the beat. They are fully clothed throughout in hip attire and sunglasses. But the women appear without mandatory head scarves.
The scenes alternate between a rooftop with a view of Tehran's signature Milad Tower, a balcony, a courtyard, a staircase and an apartment. None of the scenes were filmed on public streets.
"We have made this video as Pharell William's [sic] fans in 8hrs, with iPhone 5s," the video makers stated in English at the end of an almost five-minute clip posted on YouTube. " 'Happy' was an excuse to be happy. We enjoyed every second of making it. Hope it puts a smile on your face."
The credits at the end of the clip contain the full names of individuals identified as the art director and costume designer, along with the first names of other participants.
Last year, President Hassan Rouhani stated publicly that "happiness is our people's right," a comment that was widely reported at the time.
Rouhani was elected last year in a surprise upset against a number of hard-line candidates. He is considered a moderate and has vowed to liberalize some aspects of Iranian society, though he has met fierce resistance from hard-liners.
The Islamic Republic has long endured a culture war between hard-liners and liberalizers, who are demanding full access to the Internet, among other reforms. Internet users in Iran face considerable filtering, as well as irregular service.
In a speech last weekend, Rouhani defended people's right to the Internet and assailed using "cowardly methods" to block access to Web, the Reuters news agency reported.
But conservatives appeared defiant about the arrest of the alleged video participants.
"Trusting the youth is different from closing homes to the poison of the virtual and cyber world," Ayatollah Sadegh Larijani, the head of Iran's judiciary, was quoted as saying. "We should follow the law in preventing the enemy from misusing the innocence of families."