The Regional Transport Office or District Transport Office or Regional Transport Authority (RTO/DTO/RTA) is the organisation of the Indian government responsible for maintaining a database of drivers and a database of vehicles for various states of India. The RTO issues driving licences, organises collection of vehicle excise duty (also known as road tax and road fund licence) and sells personalised registrations.
Along with this, the RTO is also responsible to inspect vehicle's insurance and clear the pollution test.
You can file RTI to obtain information regarding the four wheeler to the concerned Regional Transport authority, where the vehicle is registered.