The investigation by the office of the Director General of Investigation & Registration follows a complaint by a customer.
"We have been getting responses from mobile service operators," said a senior government official who did not want to be identified.
SMSes account for nearly 10 per cent of the revenue for mobile service providers. The official said even a small number of SMSes not delivered but paid for would amount to a large sum given the popularity of the service among the huge subscriber base of 392 million.
If investigations indicate "unfair trade practices", a case will be registered against the service providers. MRTPC, a quasi-judicial body, will then adjudicate on the matter.
In the notice sent to mobile companies, the MRTPC arm has sought details of server capacities, the number of messages sent on special occasions including festivals and New Year's Day, the number not delivered, and how the whole thing is monitored.
A lawyer representing GSM operators told Business Standard,"The companies would have given their view that when a message is sent work is done by the operator to try his level best to deliver the message. However, after repeated attempts if the receiver's phone is switched off or out of coverage area, the service provider cannot be held responsible."
He said replies submitted by companies would now be considered by MRTPC and subsequently the complaints might be dismissed or the companies might be required to furnish more details.
