The potentially embarrassing revelation can further dent the media tycoon's hope of acquiring full control over satellite broadcaster BSkyB, The Independent reported.
In a statement, Sky News said that in one case it broke into emails belonging to Anne and John Darwin, the so-called "canoe couple" who became notorious in Britain after the latter faked his own death in a boating accident as part of an elaborate insurance scam.
The case drew a surge of media interest after John Darwin walked into a London police station in late 2007.
Claiming to have amnesia, he said he could remember nothing since 2000 but his story unraveled as journalists and police started digging.
Sky News didn't identify which story was the result of hacking.
But in an article dated July 21, 2008, journalist Gerard Tubb said the channel had uncovered documentary evidence showing that John Darwin had decided to come back to England because he was having trouble staying in Panama.
"We discovered an email," the article begins, without giving any explanation of how the message was obtained.
Sky News said the emails were later handed to police.
In a statement Thursday, John Ryley, head of Sky News, said that "we do not take such decisions lightly or frequently" and said the investigation had served the public interest.