The group had been released after "receiving education and counselling service," it quoted Defence Minister Siraj Fegessa as saying.
The minister did not say how many people are still in detention.
On 20 October, the BBC reported that more than 2,600 people had been arrested under the state of emergency, which was imposed on 9 October after a wave of anti-government protests.
Opposition groups have been demanding greater political freedom in a country ruled by the Ethiopian People's Revolutionary Democratic Front since 1991.
More than 1,500 weapons had also been recovered by the security forces.