The United States is now using drones and manned surveillance aircraft over Nigeria in the search for the hundreds of schoolgirls kidnapped by Boko Haram . But signs of them are yet to emerge , and the task is complicated by the possibility that the girls have been separated into groups . The United States , which is supporting the Nigerian government 's efforts , will continue to deepen its efforts , Defense Secretary Chuck Hagel said Wednesday while traveling to Saudi Arabia . However , `` I have seen no intelligence come back that I am aware of that shows that we 've located those girls , '' he said . The assets provide some of the best tools to try to find the girls , but the Nigerian government has shown some reluctance to use U.S. help . For now , the United States is not sharing raw intelligence from its surveillance aircraft with Nigeria 's armed forces because the countries have still not established the intelligence-sharing protocols and safeguards needed for an intelligence-sharing agreement , Pentagon spokesman Col. Steve Warren said . That said , the intelligence gathered through the surveillance flights is being fed to an interdisciplinary team on the ground , and that team is analyzing it and providing advice to the Nigerian government , he said . Warren added that the manned and unmanned aircraft being used are unarmed . U.S. Secretary of State John Kerry called the kidnapping of hundreds of girls an `` unconscionable crime , '' vowing to do `` everything possible to support the Nigerian government to return these young women to their homes and to hold the perpetrators to justice . `` I will tell you , my friends , I have seen this scourge of terror across the planet , and so have you . They do n't offer anything except violence , '' he said in a statement . `` They just tell people , 'You have to behave the way we tell you to , ' and they will punish you if you do n't . '' Pressure to find the girls . Wednesday marked one month since the 276 girls were abducted from Chibok by Boko Haram . A worldwide campaign to `` bring back our girls '' has spread awareness of the incident , and as the days go by , the pressure to find them increases . At least four Nigerian soldiers died in an ambush Wednesday as they were returning from patrol duties in Chibok , the Nigerian military said . U.S. Sen. John McCain , R-Arizona , is among those who support American military intervention to find the girls , if needed . `` You know , it 's interesting to me that when a ship is hijacked and taken into custody by these pirates , we have ... no reservations about going in and trying to take that ship back and the crew that 's being held , '' he said . `` We have no compunctions about that . '' When it comes to the hundreds of girls who were kidnapped , the response has dragged , he said . A U.S. military operation `` could be done in a way that is very efficient , but for us not to do that , in my opinion , would be an abrogation of our responsibilities , '' McCain said . Two senior administration officials told CNN that it is premature to talk about a special operations incursion into Nigeria because the girls have not been found yet . The U.S. military is there to advise and assist , but not to actively participate , the sources said . If the girls are found , it would be up to the Nigerians to devise a plan and execute it with U.S. assistance , the sources said . And that raises other complications . The Nigerian military is capable of carrying out a rescue operation , but there are concerns because it has been heavy-handed in the past and killed many civilians , the sources said . As it currently stands , U.S. law prohibits the U.S. military from working with Nigerian military units that have been accused of abuses , a senior State Department official said . `` We 've been very clear about our concerns about the Nigerian reports of and evidence of abuses by the Nigerian military , '' the official said . Even with all of these complications , the U.S. is committed to doing everything it can to find the girls , the official said . Separately , Nigerian President Goodluck Jonathan is not considering swapping Boko Haram prisoners for the kidnapped girls , according to media reports , which cited Mark Simmonds , Britain 's Africa minister , who met with the President . The director of Nigeria 's National Orientation Agency , a government information ministry , had previously said negotiations could be an option .
At least four Nigerian soldiers are killed in an ambush . Kidnapping of schoolgirls an `` unconscionable crime , '' says Kerry . The United States is using drones and manned surveillance aircraft in Nigeria . Concerns about intelligence sharing and civilian deaths complicate the situation .