Police stormed a house in the Nile Delta province of Menoufia, where group members allegedly were meeting on Friday night, the official, speaking on condition of anonymity because he was not authorised to speak to the press, said on Saturday.
The group, however, claims that the 17 were having dinner together at the house, about 65km north of Cairo.
Hundreds of Muslim Brotherhood members were arrested in March during a wave of demonstrations against the extension of Egypt's emergency laws and in support of two pro-reform judges, who were facing a disciplinary trial for revealing parliamentary election fraud.
Eighty Brotherhood members remain in jail from the spring roundups, the group said.
The Brotherhood, which is formally banned but usually tolerated in Egypt, won nearly a fifth of the parliament seats in last year's elections, making it the largest opposition group.
Founded in 1928 and banned since 1954, the Brotherhood is believed to have tens of thousands of followers.