The United States has expressed scepticism that more than 200 schoolgirls held by Boko Haram militants have been located by Nigeria, saying it has no "independent information" on the matter.
Nigeria's highest ranking military officer said on Monday that his country had located the missing teenagers, kidnapped in mid-April by the armed militant group.
But a day later, US State Department spokeswoman Jen Psaki told journalists there was no "independent information from the United States to support these reports".
Asked whether she found it "smart" of Nigerian officials to announce they had found the girls - in the event they had been located - Psaki said "for the girls' safety and wellbeing, we certainly would not discuss publicly this sort of information".
The US, with 80 US military personnel sent to neighbouring Chad for intelligence, surveillance and reconnaissance, is the biggest foreign participant in the effort against Boko Haram.
Washington has also deployed surveillance drones, spy planes and about 30 civilian and military specialists to support Nigeria's security forces.
US authorities have previously expressed doubt Nigeria has the capacity to conduct the rescue mission.
State Department and Pentagon officials as well as members of Congress have chided Nigeria for what they called a slow response to the crisis and for human rights violations of which its army is accused.
