Junior school pupils in Tanzania experienced a mass fainting fit while taking their final year exams, an educational official has told the BBC.
The 20 girls at Ali Hassan Mwinyi School in Tabora started fainting after finishing their first paper.
"I'm not a specialist but I imagine this was a case of mass hysteria that does happen in some of the schools," Midemo Paul Makungu said.
He said it only affected the girls, some of whom took 40 minutes to revive.
"There was chaos, crying, screaming, running after that first paper," Mr Makungu, Tabora's educational officer, told the BBC News website.
More than 140 Standard Seven pupils were taking the national exam at the school in the north of the country.
He said special arrangements were made so that those who had fainted could finish the other two papers they had that day.
"They eventually finished at 11pm," he said.
It is not the first such incident at the school - over the last month there have been several mass fainting fits amongst the girl pupils.
"Normally this happens in girls' secondary schools. It is very common here," Mr Makungu said.