"We have arrested Ravindra Konduskar, Nasir Sangli and Ayub Makangar. They have been remanded in judicial custody," said a DRI official.
Ravindra is the brother of Abhijit Konduskar, the owner of Konduskar Travels, a passenger transport firm.
Yesterday, following seizure of 405 kg of the psychotropic drug mephedrone, DRI had detained Ravindra and three others for questioning.
DRI had intercepted a vehicle on the Mumbai-Pune Highway on the basis of intelligence that it was transporting mephedrone from Islampur near Sangli to Mumbai.
It was reportedly manufactured at Islampur-based Omkar Industries, which is owned by Ravindra.
The factory was searched subsequently and another 355 kg of mephedrone was recovered.
Makangar allegedly oversaw the operations there.
