KADUNA, Nigeria, Sept 18 (Reuters) - Bandits have released 10 more students kidnapped two months ago from a Baptist school in northwest Nigeria, the school administrator told Reuters on Saturday. The Reverend John Hayab, administrator of the Bethel Baptist High school, said 21 students from the school remained in captivity. He said an undisclosed ransom was paid to release eight students while another two were set free due to ill health. Last month bandits released 15 students from the school after a group of 28 was set free in July following the release of a first group of 28 two days after the raid. read more Around 150 students were missing after armed men in July raided the school in Nigeria"s Kaduna state, the 10th mass school kidnapping since December, which authorities attributed to criminal gangs seeking ransom. read more "They are looking for more money, that"s why they are releasing them in batches," Hayab said. He has previously said the abductors were seeking 1 million naira ($2,433) per student. read more Schools have become targets for mass kidnappings for ransom in northern Nigeria by armed groups. Such kidnappings in Nigeria were first carried out by jihadist group Boko Haram, and later its offshoot Islamic State West Africa Province, but the tactic has now been adopted by other criminal gangs. The United Nations children"s agency UNICEF said on Wednesday that 1 million Nigerian children could miss school this year as the new term begins amid a rise in mass school kidnappings and insecurity. read more ($1 = 411.00 naira)