After bringing Mr Dinakaran from Delhi and conducting searches at his residence, the Crime Branch police personnel also grilled some others who allegedly had knowledge about the money transaction, the police sources said.
Mr Dinakaran was arrested on April 25 for allegedly attempting to bribe an unidentified EC official to get the undivided AIADMK's 'two leaves' election symbol for his faction.
The police had earlier arrested Sukesh Chandrasekar, who had allegedly struck a deal for Rs 50 crore to help the AIADMK (Amma) faction keep the two leaves symbol, and seized Rs 1.3 crore from him.
A Delhi court had remanded Mr Dinakaran to five days' police custody following which he was brought here.
The Delhi police after questioning the suspects asked some of them to appear again at the Central Government Office Complex, 'Rajaji Bhawan,' at Besant Nagar here, they said.
Besides, the police team visited various areas, including Adambakkam and Kolapakkam in Chennai, to question some persons, whose identity has not been disclosed.
The sources said that evidence was being gathered to sequence the Chennai-Delhi money trail, its alleged link to Mr Dinakaran, and how cash was routed through alleged hawala operators including Mr Faisal and Mr Naresh. The latter was arrested yesterday.
With the arrest of Mr Naresh, it was now only about "joining the dots" and the Delhi Police was trying to conclude the probe ahead of producing Mr Dinakaran before a court in the national capital when his five-day custody ends, the sources added.
Mr Dinakaran continued to be housed in the Central Government Guest House in Rajaji Bhawan and was being confronted with the "developments" in the case, the police said.
The Delhi Police team declined to comment on the progress in the case.
A security blanket has been thrown around the Rajaji Bhawan complex with a posse of police personnel led by an assistant police commissioner guarding the entry points to the guest house. Journalists were not allowed to enter inside.
Mr Naresh was detained at the Delhi Airport for involvement in "illegal transfer" of money to Chandrasekhar by Mr Dinakaran.