The detainees -- among them Dr. Hesham Khafagy, the husband of female Brotherhood candidate Huda Ghaneya -- will remain in police custody for a period of 15 days until an investigation is carried out.
The Muslim Brotherhood's lawmakers, who run as independents, hold 88 seats in the 454-seat parliament.
Egypt's largest opposition movement was founded in 1928 by Hasan al-Banna following the collapse of the Ottoman Empire.
The Brotherhood grew as a popular movement over the next 20 years, encompassing not only religion and education, but also politics, through the Party of the Muslim Brotherhood.
It blamed the Egyptian government for its passive response to the Zionists and joined the Palestinian side in the resistance against Israel.
The religious-political organization has been banned since 1954 but has continued to operate and is Egypt's most powerful opposition movement.
The Brotherhood advocates the implementation of Islamic law but says it wants democratic reforms in Egypt, where President Hosni Mubarak has had a quarter-century of authoritarian rule.
The government accuses the Muslim Brotherhood of seeking to take over the country and has passed a series of constitutional amendments in an attempt to further curtail the Brotherhood's ability to participate in politics.
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