The Indian Coast Guard on Saturday said a ship searching for the missing Dornier has picked up intermittent signals likely to be from a sonar locator beacon of the missing aircraft. Survey ship INS Sandhayak, undertaking a sub-surface search, detected intermittent transmission of 37.5 khz, likely to be from the sonar locator beacon of the missing aircraft, the Coast Guard said in a statement issued here. "The transmission is from around the position where the air traffic control radar lost contact of the aircraft on Monday night. The submarine INS Sindhudhavaj is likely to reach the area late Saturday evening for further augmentation of sub-surface search," the statement said. A multi-colour sheen of oil in concentric circles was sighted in the search area, indicating oozing of oil, the coastal security agency said. "The oil sample has been sent to laboratory for analysis," it said. Ever since the Coast Guard aircraft with three crew members went off the radar around 9.23 p.m. on Monday, an intensive search is on for the last five days to located it. The Coast Guard also requested Reliance India Ltd to extend services of a multi-support vessel with remote-operated underwater vehicle for underwater search. National Institute of Ocean Technology's research vessel Sagar Nidhi was likely to arrive in the search area on June 14 to augment the search. The missing Dornier had on board Deputy Commandant Vidyasagar as pilot, his co-pilot and Deputy Commandant Subash Suresh and navigator/observer M.K. Soni - all in their 30s. The missing aircraft was deployed for surveillance along the Tamil Nadu coast and over Palk Bay. It took off from Chennai airport around 6 p.m. on June 8 for a surveillance sortie but did not return. The last contact with the aircraft was at 9 p.m. on Monday while its last known location, as per Trichy radar, was off Karaikal in Puducherry where it was tracked till 9.23 p.m., 95 nautical miles south of Chennai. "The aircraft was the latest induction in the Coast Guard inventory in 2014 and was being flown by a highly experienced crew," an official statement said. The latest incident comes within months of a Dornier-228 of the Indian Navy with three crew going down in the Arabian Sea off the Goa coast, killing two. The March crash was the first involving a Dornier, inducted by the navy in the mid-90s. With IANS