Western diplomats say satellite images reviewed by the International Atomic Energy Agency show trucks and earth-moving vehicles at an Iranian military site, providing further clues that Iran may be trying to clean up its Parchin facility, southeast of Tehran, before allowing inspections by U.N. nuclear watchdog teams.

The diplomats, who all requested anonymity, said they suspect attempts at sanitization because some vehicles at the scene appeared to be haulage trucks and other equipment suited to carting off potentially contaminated soil from the site. Nuclear experts accredited to the IAEA has already identified Parchin as the location of suspected nuclear weapons-related testing.

The images, provided by member countries to the IAEA, are recent and constantly updated.

Iran denies allegations it is attempting to develop atomic weapons and says its nuclear activities are meant purely to generate power or for research purposes.

The diplomats spoke ahead of a meeting of the IAEA board Thursday focusing on Iran's defiance of United Nations Security Council demands to end uranium enrichment and dispel other suspicions that it may be seeking nuclear weapons.

On Tuesday, EU foreign policy chief Catherine Ashton said the five permanent members of the Security Council and Germany had agreed to quickly resume negotiations aimed at curbing Iran's nuclear work. Her announcement was a response to a February letter from Iran asking for negotiations at the “earliest” opportunity.

IAEA expert teams trying to probe the suspicions of secret weapons work by Iran tried – and failed – twice in recent weeks to get Iranian permission to visit Parchin. Tehran then said on Monday that such a visit would be granted.

Attention most recently focused on Parchin several days ago, when senior IAEA officials first spoke of unexplained activities at the site without saying what they could be and said an inspection of buildings there was taking on added urgency.