In the Sharqiyah raid, Egyptian forces stormed the home of Hossam Mohammed Abdel Salam and arrested 14 Muslim Brotherhood members on charges of holding a secret meeting and of being in possession of secret documents.
The Muslim Brotherhood is the largest and best organised opposition movement in the country, but it is also officially banned, leaving it open to periodic crackdowns.
Last week, the Supreme Administrative Court upheld a decision to have 40 members of the group tried by a military court.
The 40, including Khayrat al-Shater, the group's financier and third-ranking official, are accused of money-laundering and financing a banned organisation.
The group controls one-fifth of the parliament after fielding candidates as independents in the 2005 elections.
The Muslim Brotherhood announced in April it would field 20 candidates despite constitutional amendments approved in March that prohibit political activity on a religious basis.