At least 11 children died when their boat capsized on Sunday in northwest Pakistan, a local police official said.
All of the dead so far recovered from Tanda Dam lake, near Kohat in Khyber Pakhtunkhwa province, were between seven and 14 years old, according to local police official Mir Rauf.
Rauf said 11 children had been rescued from the water, with six in critical condition. The boat was carrying between 25 and 30 students on a day trip from a local madrassa when it overturned.
A rescue operation is underway.
Mass drownings are common in Pakistan, when aged and overloaded vessels lose their stability and pitch passengers into the water.
Many in the country do not know how to swim, particularly women who are discouraged from learning owing to conservative social mores. Their all-covering clothes also weigh them down once they become sodden.
In July, 18 women drowned when an overcrowded boat carrying a wedding party across the Indus river in Punjab province capsized.