UN inspectors found "nothing to be worried about" in a first look at a previously secret uranium enrichment site in Iran last month, the International Atomic Energy chief said in remarks published on Thursday.
Mohamed ElBaradei also told the New York Times that he was examining possible compromises to unblock a draft nuclear cooperation deal between Iran and three major powers that has foundered over Iranian objections.
The nuclear site, which Iran revealed in September three years after diplomats said Western spies first detected it, added to Western fears of covert Iranian efforts to develop atom bombs. Iran says it is enriching uranium only for electricity.
ElBaradei was quoted in a New York Times interview as saying his inspectors' initial findings at the fortified site beneath a desert mountain near the Shi'ite holy city of Qom were "nothing to be worried about".
"The idea was to use it as a bunker under the mountain to protect things," ElBaradei, alluding to Tehran's references to the site as a fallback for its nuclear program in case its larger Natanz enrichment plant were bombed by a foe like Israel.
"It's a hole in a mountain," he said.
The IAEA has declined to comment on whether the inspectors came across anything surprising or were able to obtain all the documentation and on-site access they had wanted at the remote spot about 160 km (100 miles) south of Tehran.
Details are expected to be included in the next IAEA report on Iran's disputed nuclear activity due in mid-November.
The inspectors' goal was to compare engineering designs to be provided by Iran with the actual look of the facility, interview scientists and other employees, and take soil samples to check for any traces of activity oriented to making bombs.