Britain investigating whether leaked trade papers were hacked - sources

British cyber security officials are investigating whether classified UK-U.S. trade documents that were shared online ahead of Thursday's election were acquired by hacking or were leaked, two sources told Reuters.Britain's opposition Labour Party seized on the documents, saying they showed Prime Minister Boris Johnson's Conservatives were plotting to sell off parts of the state-run National Health Service (NHS) in trade talks with U.S. President Donald Trump.Johnson has repeatedly denied that cl