Khalid Chisti was arrested late Saturday for allegedly planting pages of the Koran into a bag of ashes and trash the girl, Rimsha Masih, was taking to a garbage bin, the Los Angeles Times reported Sunday.
The 14-year-old has been held in adult jail in Islamabad since Aug. 16.
The case has drawn much international attention because of her age, her religious minority status in Sunni Muslim-majority Pakistan and the country's harsh anti-blasphemy law under which a person can be sentenced to death for criticizing Islam or the Prophet Muhammed, or for desecrating Islam's holy text, the Koran. Critics have said the law also is being used to persecute religious minorities.
Masih's lawyer, Akmal Waheed Bhatti, said he will push for an instant release and acquittal.
"Now we can say that there is nothing to this case," Bhatti. "The situation is clear, now that this imam has been arrested. Now there's a big chance that Rimsha will be released on Monday."