The UN nuclear watchdog has discovered traces of processed uranium at a second site in Syria,
the agency said on Friday, heightening concern about possible undeclared atomic activity in the Arab state.
The International Atomic Energy Agency has been examining U.S. intelligence reports that Syria almost built a North Korean-designed nuclear reactor meant to yield weapons-grade plutonium before Israel bombed it to rubble in 2007.
Inspectors who found uranium particles at the remote desert site a year ago also found similar traces at a small research reactor in the capital Damascus which the IAEA knew about and checks once a year, a IAEA report said. These traces were different from Syria's declared nuclear material inventory.
The IAEA said in February that inspectors had found enough traces of uranium in soil samples taken from the bombed site a year ago to constitute a significant find.
Friday's report said "anthropogenic natural uranium particles" had also turned up in environmental swipe samples taken from hot cells of the Miniature Neutron Source Reactor (MNSR) facility in Damascus.
Syria, told of the IAEA's discovery last month, sent a written response to the IAEA on Monday. But this did not not address the presence and origin of the particles and the UN watchdog was investigating a possible connection with the uranium particles found at the bombed site, the report said.
The IAEA said previously satellite pictures taken before the Israeli bombing revealed a building resembling a reactor.
But the new report said Syria, citing national security, was still ignoring IAEA requests for wider access and documentation to back up its assertion that Israel's target at Dair Alzour was a conventional military building.
The IAEA again urged Syria to provide additional data and trips to Dair Alzour and other, allegedly related locations to allow test-sampling of destroyed or salvaged equipment and debris removed before investigators were let into the country.
"It is clearly in Syria's interest to render to the agency the necessary cooperation and transparency if it wishes the agency to be able to corroborate its assertion about the nature of the Dair Alzour site," the report said.
Syria's only declared nuclear site is the old research reactor and it has no known nuclear energy-generating capacity.
The report said Syria was also refusing to discuss satellite pictures the IAEA had offer to share with it. Syria had provided information regarding procurement of certain equipment and materials including a large quantity of graphite and large quantities of barium sulphate", a compound sometimes used as a radiation shield in nuclear structures.
Syria had indicated the procurement efforts were civilian and non-nuclear, relating to water purification, the steel industry and shielding material for radiation therapy centers. It has claimed that the uranium particles retrieved from samples taken at Dair Alzour came from depleted uranium used in Israeli munitions, an assertion dismissed by the IAEA.
Syria has also suggested IAEA analyses were faulty and that satellite imagery Washington gave to the IAEA was fabricated.
Vienna diplomats said in March that Syria had told the IAEA it had built a missile facility on the desert tract hit by Israel,
a disclosure apparently meant to reinforce the Syrian refusal to grant more IAEA access on national security grounds.