Pakistan's president has called on officials to explain the arrest on blasphemy charges of a Christian girl with Down syndrome.
The girl -- reportedly just 11 or 12 years old -- allegedly burned pages inscribed with verses from the Koran.
Police said the girl, Rimsha, was arrested in a Christian slum of Islamabad on August 16 and remanded in custody for 14 days.
A crowd of angry Muslims had demanded she be punished.
State-run media reports said President Asif Ali Zardari has taken "serious note" of the case and called on the Interior Ministry to submit a report.
Some reports suggested the girl had been burning papers collected from the rubbish for cooking when someone entered her house and accused the family of burning pages inscribed with verses from the Koran.
Rimsha's house was locked from the outside on August 20 and no one was at home, a reporter for the AFP news agency said. Neighbors were reluctant to speak about the incident, saying that they had not witnessed the alleged desecration themselves.
A senior official of the All Pakistan Minorities Alliance, Tahir Naveed Chaudhry, told AFP that Christians who fled for shelter with relatives elsewhere in Islamabad were now gradually returning to the slum called Mehrabad.
The girl has Down syndrome -- a condition which causes various degrees of learning difficulties -- and is not yet a teenager.
The Women's Action Forum, a leading Pakistani organization fighting for the rights of women, condemned Rimsha's arrest.
Spokeswoman Tahira Abdullah demanded her immediate release and expressed outrage at the "total inhumanity" of the men who lodged the case with police.
The 2011 assassinations of a leading Pakistani politician and a Christian cabinet minister have been linked to their public opposition to strict antiblasphemy laws. They had taken up the plight of a Christian mother sentenced to death for blasphemy in late 2010. She remains in prison.
The murders renewed concerns about religious intolerance in Pakistan, where minority groups have faced numerous attacks by militants of the Sunni Muslim majority.
Last month, a mob snatched a mentally unstable man from a village police station and beat him to death in central Punjab Province after he allegedly burned pages from a Koran.
Under the blasphemy laws, a conviction for defaming Islam or desecrating the Koran can be punishable by death.
With reporting by AP and AFP