Hong Kong (CNN) -- The World Health Organization is helping the Cambodian Ministry of Health investigate the cause of a mysterious illness that has killed dozens of children in the country since April.
A joint statement from the WHO and the ministry, released Wednesday, said 61 of 62 children admitted to hospital had died from the disease. The majority of the reported cases came from southern and central Cambodia.
"[The Ministry of Health] and WHO are currently investigating the cases," Mam Bunheng, the Cambodian minister of health, said in the statement, "possible causes of the disease are being considered, but definite identification of the cause and source may take some time."
Initial reports from the Cambodian government indicate that the unknown illness struck children under seven years old.
"The symptoms include a mixture of respiratory illnesses, fever and generalized neurological symptoms, including convulsions in some of the patients," Dr. Nima Asgari, a team leader of the WHO country office in Cambodia, said in an email to CNN.
The children were brought to hospitals in the capital, Phnom Penh, and the northern tourist hub of Siem Reap -- the two biggest cities of Cambodia -- but most of them died within 24 hours upon admission.
"This can be a mixture of a number of known diseases -- virological, bacterial or toxicological -- which have been reported as one syndrome or something new," Asgari added.
"While the labs are excluding the various pathogens, we are providing support to [the Ministry of Health] to make sure that an in-depth analysis of cases is done to identify possible causes or exposures which will give us a better picture. The investigation is ongoing."
So far, there were no signs of contagion or clusters of cases -- patients who had contact with each other and fell sick together -- a telltale warning sign of a highly infectious disease. But Asgari admitted the high mortality rate in such a short time was extremely worrying.