Three members of the gang -- Prashant Kumar, Ankit Kumar and Resham Pal -- have been arrested. 

The gang offered to provide exam aspirants special vests fitted with wiring and hooked to a central command system. One of them supplied the answers, using the phone conference mode.

Superintendent of Police (City) Shailesh Kumar Pandey said gang leader Prashant Kumar collected ₹3 lakh per aspirant for the "special baniyan" -- ₹20,000 initially for the vest, ₹80,000 at the time of the exam and ₹2 lakh after selection.

The gang members had come to Mathura on Saturday to help their 'clients' in the Staff Selection Commission (SSC) examination on Sunday.

Among the clients were more than a dozen aspirants from Agra, Kanpur and other neighbouring districts.

The three arrested have been charged with cheating and forgery under relevant sections of the Indian Penal Code and under the Information Technology Act.

Acting on a tip, police raided a guest house and arrested the three on Saturday evening.

Cash, 30 electronic vests with ear phones, 25 button cells, mobile SIM cards, chips, antennae wired with a microphone, were seized from their possession, police said.

"This was the first time that the gang was going to use this high-end technology, but were nabbed in the nick of time, before the examinations," said Pandey.

"Earlier, they were involved in impersonation cases which we are investigating. The equipment was cleverly implanted in the vests and so you couldn't make out from outside what was being sneaked into the examination hall," he said.