Raisabari police have detained three contractors and recovered Rs 15 lakhs in cash from them.
The contractors have been identified as Amit Bhowmik, Sumon Majumder and Arjun Debnath.
They were on their way in a vehicle from Agartala to Raisabari in Gandachhara sub-division on Wednesday when the police intercepted them.
According to sources, these three contractors were on their way to deliver ransom money to National Liberation Front of Tripura (NLFT) militants, though the police have not yet confirmed this.
The police also arrested Ranjit, a NLFT collaborator on information gathered after questioning the contractors.
Ranjit worked as a middleman and was supposed to collect the extortion money from the contractors on behalf of the militant outfit.
NLFT cadres had also abducted three workers from Ganganagar of Gandachhara subdivision in Dhalai district in December last year.
They had been engaged in constructing a wire fence along the Indo-Bangla international border in Gandachhara when they were abducted.
The banned outfit has reportedly been demanding extortion money from the construction agencies and contractors of the area.