Cairo ? Egyptian authorities detained 31 members of the banned Muslim Brotherhood on Monday, police said, bringing to nearly 700 the number of members arrested since a crackdown began in March.

The men were arrested in Marsa Matrouh, a vacation town on the Mediterranean coast 325 miles from Cairo. All were originally from the port city of Alexandria and were on a summer holiday, according to the group’s Web site.

They were arrested for holding illegal meetings in three apartments, police officials said on condition of anonymity because they were not authorized to speak to the media.

Founded in 1928 and banned since 1954, the Muslim Brotherhood is Egypt’s largest Islamic group. Membership is considered illegal, but the group is believed to have tens of thousands of followers.

The group increased its seats in Egypt’s parliament sevenfold in last year’s legislative elections, despite clashes between security forces and opposition voters that killed 14 people. It now holds 88 seats in parliament – well short of a majority.