Police in the port city of Karachi said the student was taken into custody following a complaint from the head of the education examination board who allegedly found the remarks on the student's answer sheets, the Daily Times reported.
Pakistan's blasphemy law has been much in the news following the assassination early this month of Salman Taseer, the governor of Punjab province. Taseer, a prominent leader of the ruling Pakistan People's Party and a noted liberal, allegedly was killed by one of his security guards for seeking reforms in the law.
Under the law, a person can even be sentenced to death for criticizing Islam, the Koran or Prophet Mohammed.
The Daily Times report quoted a police official as saying the student's answer sheets were obtained before he was taken into custody and that the accused had since written an apology statement.
The Express Tribune reported a judicial magistrate ordered the student be sent to a juvenile detention center. The report said the student told investigators he had became troubled after discussing issues with his cousins visiting from Norway.