The Indonesian Army detected underwater movement at 2.5 knots around the last location of the submarine Nanggala-402 missing during a torpedo firing exercise in waters north of Bali Island, according to an official source on Thursday.
"The contact then lost, so there is still not enough data to identify that it was a submarine," said the military spokesperson Achmad Riad.
A helicopter and two military vessels also found the oil spill and the smell of diesel fuel at several different locations, but it is not yet possible to conclude that this is submarine fuel, Riad added.
The authorities have deployed six military vessels and a helicopter to search in the last position of the submarine detected, including the underwater oceanographic vessel Rigel.
In addition, the Singapore Swift Rescue vessel is expected to arrive in Bali waters on Saturday to assist the search and rescue operation, while the Rescue Mega Bakti Malaysia ship will arrive next Monday.
Offers of assistance also came from the United States, Germany, France, Turkey, India, Russia, and Australia, added Riad.
The submarine Nanggala-402 lost contact in the waters north of Bali Island during a torpedo firing exercise in the early hours of Wednesday, with its last position at about 60 miles north of the tourist island.
Produced by Howaldtswerke Germany, the Nanggala-402 weighs 1,395 tons, 59.5 meters long, 6.3 meters high, and 5.5 meters wide with an arsenal of up to 14 Surface and Underwater Target (SUT) torpedoes. It joined the Indonesian Navy in 1981.