Sources in it said that the ED, which is probing the money laundering aspect of the Narada sting operation, had submitted the chargesheet against the five in the special court earlier in the day.
The central agency also pointed to the presence of the state's Law Minister Moloy Ghatak in the Bichar Bhavan premises, within which the CBI court is located, quoting media reports.
Adhikari, a former minister in the last Mamata Banerjee-led government, had joined the BJP just before the 2021 assembly elections.
Mitra was arrested along with West Bengal ministers Subrata Mukherjee and Firhad Hakim and former Kolkata mayor Sovan Chatterjee on May 17.
It heard the CBI plea for transfer of the case from lower court to high court, and applications filed by the accused for recall of the stay order the high court had given on a lower court ruling.