WASHINGTON — The United States has sent 80 troops to Chad in Central Africa to support a growing international effort in neighboring Nigeria to help find and rescue the schoolgirls who were abducted by an Islamist extremist group last month, the White House said on Wednesday.

The American military personnel are not ground troops. They are mostly Air Force crew members, maintenance specialists and security officers for unarmed Predator surveillance drones that will help search for the more than 260 Nigerian girls seized by the group, Boko Haram.

“These personnel will support the operation of intelligence, surveillance and reconnaissance aircraft for missions over northern Nigeria and the surrounding area,” the White House said in a statement formally notifying Congress about the deployment.

For the past 10 days, the United States military has been flying manned and unmanned surveillance aircraft over heavily forested regions in northeastern Nigeria, where intelligence officials believe the captors are hiding the girls.