Sydney, Dec 21 (IANS): Australia resolved the oldest mystery in its naval history on Thursday after discovering its first submarine, the HMAS AE1, which disappeared over a century ago, official sources reported Thursday.

The HMAS AE1 disappeared on September 14, 1914, with 35 people on board, for some unknown reasons while sailing between the islands of New Britain and New Ireland, in northeastern Papua New Guinea, reports Efe news.

The vessel was located about 300 metres deep off the Duke of York Islands by the survey ship Fugro Equator.

"The loss of AE1 in 1914 was a tragedy for our then fledgling nation," Defence Minister Marise Payne told reporters here.

""It was the first loss for the Royal Australian Navy and the first Allied submarine loss in World War I," she added.

The Fugro Equator, one of the survey ships that participated in the search for a Malaysia Airline aircraft which disappeared in 2014 in the Indian Ocean, discovered the missing submarine on the 13th expedition to find it.