Thirty-three of the 35 members of the vessel 'Seaman Guard Ohio' were escorted to Muthiapuram Police Station for questioning, police sources said.
The remaining two members of the crew, who were allowed to stay on board the ship for carrying out maintenance work, would be taken to the police station later, the sources said.
Speculation is rife that the police is preparing for the formal arrest of ten crew and 25 security guards of the vessel, against whom an FIR was filed on October 14.
A team of Government Hospital doctors has been summoned to the police station to undertake a medical check up of the crew members, indicating their imminent arrest.
Tuticorin District Superintendent of Police S Durai and Superintendent of Police of the "Q" Branch K Bhavaneeswari are supervising the modalities for the arrest.
Among the crew eight are Indians and two Ukranians. The Tamil Nadu special investigation "Q" branch, which has now been tasked with the probe, refused to share details of the on-going investigation.
The police action comes a day after the Tamil Nadu Police maintained that the impounded vessel had strayed into Indian waters and defended the Marine police action in detaining it.
The Indian Coast Guards intercepted the ship on October 12 and an FIR was registered against 35 persons onboard under the Arms Act and Essential Commodities Act for buying 1,500 litres of diesel illegally with the help of a local shipping agent.