Medical college vice-principal-cum-hospital superintendent M A Rashid today said the four, aged between two years and six years, were among six children admitted yesterday and died in the night.
All the six children had been admitted with complaints of fever, vomiting and convulsions.
The unspecified disease was first reported at the hospital on June 5.
Rashid said a total 52 children were admitted with similar complaints since the June 5 and 20 of them had died.
All the children hailed from Kaliachak area of Malda district.