"The incident happened about two weeks ago when a girl about 18 years old was accused of dropping in a mosque a document whose contents were considered to be blasphemous," Salabiu Jamiu, spokesman of Niger State police command said.
Police initially intervened locking the girl up in a cell for her own protection, but a mob then overpowered policemen at the station and killed her.
The police officer denied a report that the girl was preaching the Christian gospel to some Muslim youths. He said that she appeared insane and incoherent in her speech when interrogated.
"The girl is probably a stranger or wanderer in the village because since the incident happened, nobody has come forward with any claim identifying or knowing her anywhere," Commander Jamiu said.
He said some arrests have been made following the crime and that the investigation was ongoing.
Christians and Muslims frequently clash in Africa's most populous country, which under the constitution is secular, and isolated attacks are not uncommon.
About 10 years ago, a Christian trader, Gideon Akaluka, 26, was decapitated in northern commercial city of Kano by suspected Islamic youths who accused him of committing blasphemy against Islam.
His head was hung on a pike and paraded round the sprawling city in a show that triggered local and international condemnation.
There have also been reports of Christian preachers being attacked after sermonising in public places in Muslim-dominated parts of northern Nigeria.