From Reuters:

Accusations that a second uranium enrichment plant under construction in Iran was clandestine are “not true,” a senior Iranian official told Reuters at the United Nations on Friday.
“If it was a covert plant, we would not have informed the (International Atomic Energy) Agency,” said the official, speaking on condition of anonymity.
Iran told the agency this week that it had a second uranium enrichment plant under construction, just as six world powers and Iran prepare for rare talks on October 1.
The revelation may sharpen a standoff between the powers and Iran over its nuclear ambitions and add to Western calls to consider tougher U.N. sanctions against the Islamic Republic.
U.S. President Barack Obama and other Western leaders accused Iran of building a secret nuclear fuel plant and demanded Tehran immediately halt what he called a “direct challenge” to the international community.