your connection to The Boston Globe

Tunneling in Iran worries US officials

WASHINGTON -- The sudden flurry of digging seen in recent satellite photos of a mountainside in central Iran might have passed for ordinary road tunneling. But the site is the backyard of Iran's most ambitious nuclear facility, leading US officials and analysts to reach another conclusion: It appears to be the start of a major tunnel complex inside the mountain.

The question is, why? Worries have been stoked by the presence nearby of fortified buildings where uranium is being processed. Those structures in turn are now being connected by roads to Iran's nuclear site at Natanz, where the country recently started production of enriched uranium in defiance of international protests.

As a result, photos of the site are being studied by governments, intelligence agencies, and nuclear analysts, all asking the same question: Is Iran attempting to thwart future military strikes against its nuclear program by placing key parts of it in underground bunkers?

The construction has raised concerns at the International Atomic Energy Agency, the Vienna-based UN watchdog that monitors Iran's nuclear program.

On Friday, an IAEA spokeswoman confirmed that the agency has broached the subject with Iranian officials but declined to elaborate. IAEA officials plan to press the issue further in a previously scheduled visit to Tehran later this week.

"The tunnel complex certainly appears to be related to Natanz," said David Albright, a former UN weapons inspector and president of the Institute for Science and International Security, a Washington-based nonprofit group that provided copies of the photos to The Washington Post. "We think it is probably for storage of nuclear items."

The commercial satellite photos, taken on June 11, show two new roads leading to a construction site on the side of a mountain closest to the nuclear site's southern boundary.

Although tunnel entrances are not directly visible, the photos show rocks and debris in large piles near the dig sites. There are no signs of construction in similar photos taken of the area six months ago.