When did the Cabinet receive information about the arrests and the imposition of Emergency?

In a special meeting at 6 a.m. on 26 June 1975

Answer: In a special meeting at 6 a.m. on 26 June 1975
Cabinet was informed about the arrests and the imposition of Emergency in a special meeting at 6 a.m. on 26 June 1975.

On the night of 25 June 1975, the Prime Minister recommended the imposition of Emergency to President Fakhruddin Ali Ahmed. He issued the proclamation immediately. After midnight, the electricity to all the major newspaper offices was disconnected. In the early morning, a large number of leaders and workers of the opposition parties were arrested. The Cabinet was informed about it at a special meeting at 6 a.m. on 26 June, after all this had taken place.