South Korea has found "decisive evidence" that a North Korean torpedo sank one of its warships after analysing chemical traces found on the wreckage, a media report said Tuesday.
A multinational team investigating the March 26 sinking of the Cheonan is due to report on Thursday. South Korea has promised a "resolute response" if the North is proved to have been to blame.
"The analysis of metal pieces and traces of explosive recovered from the Cheonan and the seabed led us to secure decisive evidence that there was a North Korean torpedo attack," Yonhap news agency quoted a military source as saying.
The explosive traces have a similar chemical make-up to substances found in a stray North Korean torpedo secured by South Korea seven years ago, the source was quoted as saying.
The defence ministry refused comment before the official announcement on Thursday.
An explosion broke the 1,200-tonne corvette in two near the disputed inter-Korean border with the loss of 46 lives.
Yonhap and other media also said a fragment presumed to be part of the torpedo's propeller had been found. Dong-A Ilbo newspaper said investigators have concluded the fragment was from a torpedo made in either China or Russia.