The children that died ranged between 12 months and 4 years in age, the report said.
Police are still trying to determine what happened on board the boat, by questioning survivors.
The Europa Press news agency reported that 15 people had died and that police had assumed that their bodies had been thrown overboard.
Would-be illegal immigrants have died in the past while attempting to reach Spain from Africa.
More than 900 people died at sea in 2007 trying to reach Spain.
This number included 629 from sub-Saharan Africa, 287 from north Africa and five Asians.