A school trip to Omatua Camp, near Rissington, has resulted in about half the 30 youngsters and even some parents getting ill.
The incident, involving children from Napier Central School and their parents last week, is being investigated by public health specialists from the Hawke's Bay District Health Board.
The school's assistant principal Jane Taylor said the group arrived at the camp on Wednesday last week but days later the sickness kicked in.
A second planned school visit to the camp was cancelled as a result.
"They [health inspectors] advised us not to go until they had identified the cause of the illness," Ms Taylor said.