They were two words heard round the world by the intelligence experts and atomic inspectors who are trying to decipher the riddle of the Iranian nuclear program.

On Monday evening, the chief of Iran’s Atomic Energy Organization, Ali Akbar Salehi, told Iranian state television that he and his colleagues were “working out a timetable for the inspection” of the just revealed nuclear site outside the holy city of Qum. Then Mr. Salehi said he was preparing a letter for international inspectors in Vienna “about the location of the facility,” adding, cryptically, “and others.”

That got everyone’s attention.

Since the start of the Iranian standoff with the West seven years ago, some intelligence officials and inspectors have suspected that Tehran maintained a network of clandestine nuclear sites, projects and personnel that paralleled the nuclear program that Iran declared. Since inspectors visit the declared facilities, the thinking went, it would make little sense for the Iranians to divert fuel from them for a bomb project; the chances of being caught would be high.

So the hunt has long been on for a hidden production network that replicates the public one. The Friday revelation of the secret enrichment site outside Qum represents the first big breakthrough.

Mr. Salehi’s reference to “others” — widely interpreted in the intelligence world as meaning other nuclear sites — has given investigators guarded hope that more pieces of the Iranian nuclear puzzle may finally be coming into view.

That could start, they say, with shipments from a previously declared Iranian uranium mine near the Strait of Hormuz. Investigators have wondered about what happened to 30 to 50 tons of uranium from that mine that are unaccounted for.

But raw uranium is not the stuff of bombs. The Iranians would have to convert it into gas to move down the path to a weapon. As a result, investigators are looking anew at a set of documents obtained by Western intelligence agencies about something called the Green Salt Project, which some believe is meant to do exactly that.

Iran has previously dismissed the documents as fabrications and refused to answer questions from the International Atomic Energy Agency about them.

The project derives its name from uranium tetrafluoride, known as green salt, which is an intermediate product in the conversion of uranium ore into uranium hexafluoride. That is the gas that spinning centrifuges can enrich into fuel for nuclear reactors or, with a bit more enrichment, bombs.

There are also suggestions that the project coordinated work on high explosives that would provide the crushing force needed to start an atomic chain reaction, as well as design work for missile warheads.

“It makes a lot of sense now that they would have been working on all of these things,” one foreign intelligence official who has worked on the Iranian riddle for years said in an interview. The Qum plant, he added, “makes no sense in isolation.”

For years, the inspectors of the International Atomic Energy Agency in Vienna have struggled to persuade Iran to address the growing evidence of what they call a “possible military-nuclear dimension” to its nuclear program. Iran claims that its work is aimed solely at producing electrical power.

“It is against our tenets, it is against our religion, to produce, use, hold or have nuclear weapons,” Mr. Salehi told Iranian television. “We have been saying this,” he said, for decades.