Two Coptic Christian boys have been put in juvenile detention after locals accused them of urinating on pages of the Islamic holy book.
It is the latest in a series of legal cases in Egypt against alleged contempt of religion.
Accusations of insulting Islam have increased in Egypt – particularly against Christians – since last month's fury over an anti-Islam film produced in the United States.
Such cases occurred in the past, but the flurry to prosecute in recent weeks has raised concerns over freedom of speech and over the power of ultraconservative Islamists in the country.
The new case is a rare instance of minors being accused. The boys, aged 9 and 10, were detained on Tuesday in a southern town, to be held for 15 days while prosecutors investigate the accusations.
There have been 17 cases of alleged contempt of religion filed since the January 2011 revolution, including at least five in recent weeks, according to the Egyptian Initiative for Personal Rights.
A female Coptic teacher in another southern town was also summoned for interrogation last week and detained for a night after her students accused her of speaking offensively of the Prophet Muhammad in class.
The teacher was released from detention, but prosecutors are still investigating her, human rights activists said.
Another Coptic Christian, Alber Saber, is facing trial for posting material on his Facebook page deemed offensive of religion. He was first detained after neighbours complained he had posted the anti-Islam film, but investigators didn't find it. Nonetheless, within days he was put on trial on charges of contempt of religion. His trial began last week.
In a rare case of prosecuting an offender of Christianity, an Islamic preacher is on trial for tearing up and burning a copy of the Bible during protests last month against the film.
Charges of contempt for religion in Egypt carry a potential maximum sentence of five years in prison. Since the film, there have been calls by leaders of some Muslim nations, including Egypt, for international laws criminalising insults to religion.