By Jon Swaine
Iran may have carried out a clean-up operation at a building suspected of being used for nuclear weapons experiments within a key military facility, experts warned last night.
New satellite photographs appear to show that unusual activity has taken place in recent weeks at the Parchin site outside Tehran, according to the Institute for Science and 
International Security (ISIS).
A large stream of water pictured flowing from the building, said to feature an “explosive chamber” for testing, “raises concerns that Iran may have been washing inside the building”, according to the group.
A series of unidentified items were also shown lined up outside the building in the April 9 photographs. Pictures taken in March and in July 2011 showed neither, suggesting unusual recent developments.
David Albright, ISIS’s founder, said its finding backed up concerns at the International Atomic Energy Agency (IAEA), which has been denied access to the site since 2005, over recent “activity” there.
“Iran should immediately allow IAEA inspectors into the Parchin site and allow access to this specific building,” said Mr Albright, a former inspector. “It should also explain the purpose of the activities”.