The government is conducting an internal investigation into how files related to the Hillsborough disaster were leaked to the BBC, the home secretary has confirmed.
Last Thursday the broadcaster revealed that Margaret Thatcher was told that a Merseyside Police officer blamed "drunken Liverpool fans" for the tragedy.
The disaster saw 96 people crushed to death on overcrowded terraces in Sheffield during an FA Cup semi-final match in April 1989.
The documents, which were leaked to the BBC, show that four days after the tragedy a member of Thatcher's No 10 policy unit met senior Merseyside officers who told her that large numbers of Liverpool fans turning up without tickets had been a "key factor" in the disaster.
Speaking in the House of Commons on Monday, Liverpool Walton MP Stephen Rotheram said he was concerned there may be further leaks on a "drip-drip basis" which would undermine the Hillsborough independent panel.
Ministers insist they want the files published in an orderly fashion, with the families of those killed in the disaster seeing them first.
"Many believe this leak can only have come from a senior politician, a senior civil servant or the BBC themselves having access to this sensitive documentation," Rotheram told MPs.
May told the Labour MP that she wanted to ensure that information was shown to the families of those who died in the disaster first.
"There is a leak inquiry that has been initiated by the Cabinet Office and I share the concerns that have been expressed," she said.