PHNOM PENH, Cambodia -- Health officials in Cambodia are searching for the cause of a mystery disease that has killed more than 60 children over the past three months, the World Health Organization said Thursday.

The "undiagnosed syndrome" has killed 61 children since April, but there's no indication that is it spreading from person to person, said WHO spokeswoman Aphaluck Bhatiasevi.

She said health workers are trying to determine whether the cases were all the same disease or a collection of various illnesses.

The children were all under 10 years old and first fell ill with a high fever, followed by neurological symptoms and severe respiratory problems that quickly progressed. The cases have been reported in hospitals in 14 provinces, with most occurring in southern Cambodia.

The majority of the victims were aged younger than three, Reuters reported.

Health Minister Man Bung Heng was quoted as saying identification of the cause may take some time. Neighboring countries have also been alerted.

The United Nations agency said in a June 30 report that the clinical signs of those afflicted with the disease "appear unusual," with patients suffering from fever and a rapid deterioration of respiratory functions, although platelet counts, liver and renal functions were found normal.

No other hospital patients or staff in Phnom Penh had fallen ill with similar symptoms, WHO said.

The Associated Press and Reuters contributed to this report.

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