The manned flights are with the permission of the Nigerian government.

The United States has started surveillance flights over Northern Nigeria as part of its efforts to free the Chibok school girls.

The manned flights are with the permission of the Nigerian government.

The U.S. also clarified that it has 30 officials currently in Nigeria helping with the rescue efforts, Al-Jazeera reports. The officials include five State Department officials, two strategic communications experts, a civilian security expert and a regional medical support officer, the White House said. The officials also include 10 Defense Department planners already in Nigeria, seven extra military advisors from U.S. Africa Command, AFRICOM, and four FBI officials expert in hostage negotiations.

U.S. officials also said they believe the video released by the Boko Haram on Monday showing the abducted schoolgirls is authentic.

“Our intelligence experts are combing through every detail of the video for clues that might help ongoing efforts to secure the release of the girls,” Al-Jazeera quotes State Department spokeswoman, Jen Psaki, as saying.

“We have no reason to question its authenticity.”

The U.S., U.K., and China are among several foreign countries that have pledged assistance and have joined in the search for the girls kidnapped from their school dormitory in Chibok, Borno State on April 14.

The Boko Haram has killed thousands of people since an insurgency that began in 2009. Borno, Yobe, and Adamawa, the major areas of action of the Boko Haram, have been under emergency rule since May last year.

In Monday’s video, the Boko Haram leader, Abubakar Shekau, said he would only release the girls if the federal government releases Boko Haram prisoners across the country.

Hundreds of Boko Haram prisoners have been arrested with some being prosecuted for terrorism related activities. Some, like Kabiru Sokoto, a Boko Haram cell leader, have been convicted of terrorism.

The Nigerian government has said it is still studying the video even as civil society groups disagree on whether the government should negotiate with the Boko Haram or not.