JAKARTA (Reuters) - Lina, a former worker at a cigarette factory in Indonesia, says she was 17-years-old the first time she was possessed by an evil spirit.
"My older sister went down first. She was screaming and her body went rigid and she couldn't move. Then the spirit came into my body too," said Lina, who like many Indonesians has one name.
Reports of schoolchildren, young women and factory workers going into mass trances or speaking in tongues are common across Indonesia's vast archipelago of 226 million people.
The phenomenon may provide an outlet for stress, some experts say. In many cultures, it is part of a religious or spiritual experience, whether in the voodoo trances of Haiti, the mass hysteria of Europe's witch trials, or Christianity's exorcisms.
Earlier this month, local news station Metro TV broadcast footage of 11 students and five teachers in a mass trance at a school in the central island of Sumbawa.
Around 50 female workers at a garment factory in Tangerang, near Jakarta, went into a collective trance last June, weeping and jerking their bodies around, according to Tempo magazine.
"Every society has some kind of culturally appropriate place for trance experiences, usually in religious settings," said Tanya Luhrmann, a Stamford University anthropologist who studies witchcraft and evangelical Christianity, where such group faintings are common.
"There appears to be a contagion element to trance, but it really requires some kind of willingness on the part of the individual," she said in an emailed reply to questions, adding that this was the case even if it seemed unconscious or unwilled.
In trance, people can do and say things for which they are unlikely to be held responsible, which can be cathartic, particularly for weaker members of society, she said.
Religion, education and development have done little to budge widespread acceptance of the supernatural among Indonesia's diverse ethnic and religious groups.
"In Indonesia, trance is tied up with culture," said Lidia Laksana Hidajat, research coordinator in the psychology faculty of Jakarta's Atma Jaya University.
"We know that there are traditional trance dances in Bali but this is already a modern world. Indonesia is developing very fast but it still happens all the time," said Hidajat, who has been researching mass trance in Indonesia.
Few Indonesians are comfortable discussing their trance experiences, but Lina, now 23, said she had been possessed many times in the past six years, always by the same djinn.
"Its face is exactly the same face as my older sister but the body is hard to make out. It calls my name but if I follow it, it disappears," she said.
Lina said that mass trances were so common at the cigarette factory in Malang where she worked that she eventually quit.
Indonesian media reported a group trance among workers at Bentoel's cigarette factory in Malang, Java, in March 2006. Hidajat interviewed 30 of the affected women for her research.
"They told me that when it happened, they were sitting in a very long hall, working together in rows, rolling the cigarettes by hand," she said.
"They were working in silence. That's one of the requirements of a trance to happen -- it's usually quiet and when they are engaged in monotonous activity."
Suddenly, one of the workers started screaming and her body went stiff. The one next to her started crying and went stiff too. Others tried to help but soon they started too in a kind of domino effect.
A local Muslim leader was summoned, but his prayers had no effect. Eventually, the exhausted women fell asleep and when they awoke they remembered nothing.
Hidajat concluded that the mass trance had more to do with exhaustion and stress than evil spirits.
She says that there were many common factors between the trance victims she interviewed.
"Often they are people who are very religious or under pressure. They were also from low socio-economic backgrounds and many said they didn't have happy childhoods," she said.
"All the trance dancers I met in Bali had similar vulnerable personalities."
Eko Susanto Marsoeki, director of Malang's Lawang Psychiatric Hospital, said overwork was closely linked to mass trance incidents in factories.
"Usually this happens to people who had problems in their childhood and to people who are working too hard. It's a form of dissociation, a kind of hysteria," he said.
"They can't protest, but they can protest via a mass trance. So often it is a form of protest that will not be dealt with too harshly," he said.
When more than 30 high school students at Kalimantan's Pahandut Palangka Raya High School fell into a trance in November, they blamed a spirit living in a nearby tree.
During the morning flag-raising ceremony, one of the girls suddenly started screaming and couldn't move. Soon her friends joined in until more than 30 of them were screaming and fainting, the deputy principal Friskila told Reuters.
Some of the girls woke from the trance after a student played a Muslim prayer ring tone on her mobile phone. Others were taken by their parents to local witch doctors.
Friskila, however, favors a less superstitious explanation.
"They are bored, tired and then this happened, she said. They all got a day off school."
Editing by Sara Webb and Megan Goldin