230 people have been detained on December 21, 2017, after the State Security Force raided what have been described as a mixed-gender party in Lavasan and Farmanieh in the northern part of the capital Tehran.
They were celebrating Yalda night, one of the most celebrated traditional events in Iran which marks the longest night of the year, that is, the renewal of the sun and the victory of light over darkness.
Iranian authorities have a history of clamping down on parties. With the SSF shutting down get-togethers and arresting those in attendance.
Such restrictions have become a regular feature of Iranian life since the 1979 Islamic revolution, as members of the morality police appear on the streets, or are deployed in vans at public places, to tackle women defying the compulsory hijab, men with non-approved hairstyles, or men and women partying together.

Source » iran-hrm