Duque said their team from the National Epidomiology Center, which is conducting a periodic check on students confined at the Philippine General Hospital, are still determining if there are other students who were exposed to mercury by inhalation of its vapor.
Duque said the students were conducting a science experiment last Thursday, studying the characteristics of the metal when some of them touched or played with small amounts of mercury contained in an open beaker.
In a statement, the DOH said the school declared a holiday for the rest of the week so all exposed people, including teachers and visitors, can be tested.
Duque said proper treatment would be given to all those affected.
He said the environmental management bureau of the Department of Environment and Natural Resources would conduct its own investigation on the said incident and to contain any possible contamination of the surroundings.
The cabinet official said school officials are cooperating with the authorities over the said incident.
Duque said guidelines on the use of mercury would be reviewed so that accidental spillage would be prevented.