MANILA  The military arrested dozens of people and seized caches of weapons after martial law was imposed over the weekend in a southern Philippine province where 57 people were killed in a massacre two weeks ago, officials said Sunday.

The military has detained nearly 50 people in the province, Maguindanao, in a bid to quell a rebellion by supporters of a powerful political family accused of carrying out the massacre, said an army official, Maj. Randolph Cabangbang.

Among those arrested over the weekend were six members of the Ampatuan family, including the patriarch, Andal Ampatuan Sr., and his son Zaldy, the governor of the five-province Muslim autonomous region that includes Maguindanao. A seventh member, Andal Ampatuan Jr., had been arrested before the crackdown.

The military said Sunday that it had raided a property owned by the family patriarch and found 40 firearms, including ArmaLite assault rifles and ammunition.