Boko Haram leader Abubakar Shekau released a video Monday saying that he would be willing to trade some of the abducted schoolgirls for the release of prisoners. The 17-minute video shows about 130 girls in full veils praying in an undisclosed location. An estimated 223 girls remain missing from the 276 kidnapped in April. Shekau claims the girls in the video have converted to Islam, and he will only release the girls who haven't converted upon the release of his "brethren." "These girls, these girls you occupy yourselves with ... we have indeed liberated them. These girls have become Muslims," said Shekau. "We will never release them [the girls] until after you release our brethren. Here I mean those girls who have not submitted [converted to Islam]." International efforts have increased in the search for the missing girls. The United States, United Kingdom, Israel, and other nations have sent support to aid in finding the girls. The Nigerian government has been criticized for its slow response to the crisis and lack of effort to find the abducted students. Boko Haram, whose name translates to "western education is a sin," has attacked schools and villages in Nigeria since 2009. It was a video Boko Haram released threatening to sell the girls as slaves that motivated the international community to take action.