Japanese engineering firm Hitachi Zosen has launched an investigation after revelations that the emissions data of more than 1,000 engines had been rewritten over two and a half decades.

The company said it has found that data had been manipulated for 950 engines made by Hitachi since 1999, of which 903 were for non-Japanese-flagged vessels.

The investigation also found 414 engines made by IMEX were affected, of which 395 are for internationally flagged vessels.