With no signs of the wreckage of the Indian Coast Guard's aircraft that went missing on Monday night and no signals from the plane or from the crew's mobile phones, the search for the aircraft was intensified on Wednesday, officials said.
One survey ship of the Indian Navy and one submarine were inducted in the search operation on Wednesday, sources from the navy said.
There are now five Indian Navy and five Coast Guard ships searching for the aircraft, along with a submarine and P8I and other surveillance aircraft along with some patrol boats.
Defence ministry spokesperson Sitanshu Kar tweeted that Coast Guard Director General Vice Admiral H.C.S. Bisht visited Chennai on Wednesday to take stock of the situation and oversee the search operation.
In a statement issued here on Wednesday, the Coast Guard said the search operation for the Dornier aircraft was being augmented with naval ships with sonar to facilitate sub-surface search deployed in the area.
Air sorties have been carried out for 40 hours to locate the missing aircraft.
Asked about mobile phone tower signals from the phones of the three-member crew, a Coast Guard official told IANS that no such signals were received.
The aircraft with three crew members aboard, all in their 30s, went missing near Karaikal in Puducherry on Monday night.
The crew comprised Deputy Commandant Vidyasagar, piloting the aircraft, his co-pilot and deputy commandant M.K. Soni, and navigator/observer Subash Suresh.
The missing aircraft was deployed for surveillance along the Tamil Nadu coast and Palk Bay. It took off from the Chennai airport around 6.00 p.m. on Monday for a surveillance sortie. But it did not return.
An official statement issued on Tuesday said the last contact with the aircraft was made at 9.00 p.m. on Monday.
The last known location of the aircraft, as per the Trichy radar, was off Karaikal in Puducherry, where it was tracked till 9.23 p.m., 95 nautical miles south of Chennai.
A Coast Guard official told IANS on Tuesday night that no signal including sonar has been obtained.
"The aircraft was the latest induction in the Coast Guard inventory in 2014 and was being flown by highly experienced crew," an official statement said.
The statement also said the search area for the missing plane was now up to 70 nautical miles into the sea, extending from Mahabalipuram to Karikal on the Tamil Nadu coast.
An advisory has also been issued to fishermen and merchant ships, and coastal security group of Tamil Nadu Police is also on the lookout.
The statement added that the Subsidiary Intelligence Bureau has activated its information mechanism to "sensitise local populace".
The latest incident comes months after a Dornier-228 of the Indian Navy with three crew members went down in the Arabian Sea off the coast of Goa, killing two.
The March crash was the first of a Dornier since it was inducted into the navy in the early 1990s.