Three Singaporeans were among those detained.

All participants of the Cosplay Festival 4, a two-day event at Sunway Putra Hotel in Kuala Lumpur, have been released after being detained for seven days and have left Malaysia.

Malaysia's immigration authority, Jabatan Imigresen Malaysia (JIM), conducted a raid on March 23 at the event and 12 people were detained, including the event organiser and three Singaporeans.

The participants in the event had entered Malaysia on social visit passes.

According to JIM's website, professional visit passes are issued to foreign stage artists who wish to perform in Malaysia, and applications should be forwarded to Puspal, the Central Agencies Committee for Applications for Filming and Performances by Foreign Artistes, for approval.

The event organiser, Mr Ahmad Syafiq Nuzar Ahmad Radzi, 27, said in a Facebook post on March 29 that all 11 "international guests have been released by immigration to their respective embassies".

Some of the detained cosplayers updated their Facebook statuses with their experiences of what had happened.

According to the posts, they were placed in a cell with more than 30 people, where they had to sleep on the concrete floor without any pillows or blankets, and shared a single toilet cubicle.

Meals were served in bags three times a day, and they had to use their hands to eat as no cutlery was provided. Among the 30 in the cell were pregnant women and children.

Other than the Singaporeans, the foreigners detained were five from Japan, two from Thailand and one from Hong Kong. They received news that they could be released around 10am on March 29.

"We were overjoyed and hugged each other with tears," one of them said in a Facebook post.

She also urged other performers to be aware when going to perform overseas. "Please check with the event organiser whether they have applied for the permit for you to perform in their country."

She added: "I would not want anyone to have the same experience I had."

Investigations on the event are still ongoing.