Zubeen Garg’s cousin and Assam Police DSP Sandipan Garg was arrested on Wednesday in connection with the singer's death in Singapore last month, a senior officer said.
The DSP was booked under various sections of the Bharatiya Nyaya Sanhita (BNS), including culpable homicide not amounting to murder, criminal conspiracy, and causing death by negligence, he said.
This is the fifth arrest in the case.
Earlier, North East India Festival chief organiser Shyamkanu Mahanta, the singer's manager Siddharth Sharma, and his two band members - Shekhar Jyoti Goswami and Amrit Prabha Mahanta - were apprehended.
"We have arrested Sandipan Garg. Now, we are doing the necessary legal formalities," CID Special DGP Munna Prasad Gupta told PTI.
The apprehended police officer was interrogated several times in the last few days over the singer's death in Singapore last month.
Sandipan Garg, a deputy SP and a cousin of the singer, was present with him during the alleged drowning incident in the island country.
"Our team has taken him to a court here. We will seek police remand," another senior officer said.
The four others, who were arrested earlier in connection with the case, are now in police custody.
Zubeen Garg died in Singapore on September 19 while swimming in the sea. He had gone to the Southeast Asian nation to attend the 4th edition of the North East India Festival, organised by Shyamkanu Mahanta and his company.