File photo shows rescuers work at the site of a boat accident in Lagos, Nigeria, March 12, 2014. (Xinhua/Zhang Weiyi)

ABUJA, Aug. 3 (Xinhua) -- Twenty-one people were confirmed killed after a boat capsized in Nigeria's northwestern state of Sokoto, local authorities said on Friday.

Responders recovered the bodies of 17 women and four children on board the overloaded boat, which capsized due to strong waves in Gida Kare district of the state on Thursday, the National Emergency Management Agency said.

An investigation has been launched to ascertain the cause of the boat.

The boat was carrying at least 50 passengers at the time of the incident.

The 29 other victims were able to make it to shore during a rescue operation, said Suleiman Karim, a NEMA personnel.

One other official said a 1-year-old child was among the dead victims.

The victims of the boat accident were all internally displaced persons (IDPs) returning to their village in Gidan Kare after they were attacked recently by gunmen, according to the local Daily Trust newspaper.

Gidan Kare is one of many districts in northern Nigeria hard-hit by attackers, mostly cattle rustlers.