A Syrian site that Israeli aircraft bombed on Sept. 6 was most likely a plant for assembling a nuclear bomb, an Israeli nuclear expert said Thursday, challenging other analysts' conclusions that it housed a North Korean-style nuclear reactor.

Tel Aviv University chemistry professor Uzi Even, who worked in the past at Israel's Dimona nuclear reactor, said satellite pictures of the site taken before the Israeli strike showed no sign of the cooling towers and chimneys characteristic of reactors.

The absence of telltale features of a reactor convinced him the building must have housed something else, he said. And a rush by the Syrians after the attack to bury the site under tons of soil suggests that the facility was a bomb-assembly plant, which might have been leaking lethal doses of radiation after the Israeli attack.

Israel has maintained an almost total official silence over the strike, which Syria said hit an unused military installation. But foreign media reports, some quoting unidentified U.S. officials, have said the strike hit a nuclear facility linked to North Korea.

Damascus denies it has an undeclared nuclear program, and North Korea has said it was not involved in any Syrian nuclear project.

Last month, American analyst David Albright, president of the Institute for Science and International Security, said commercial satellite images taken before and after the Israeli raid supported suspicions that the target was indeed a reactor and that the site was given a hasty cleanup by the Syrians to remove incriminating evidence.

Albright saw a clue in the fact that the structure was roofed at an early stage in its construction.

"From what we understand, North Korea builds reactors in an old-fashioned way; the roof goes on early." he said at the time.

Other analysts have said the satellite images are too grainy to make any conclusive judgment.

But in an interview Thursday with the Haaretz newspaper — which first reported his assessment — Even compared pictures of a North Korean reactor at Yongbyon, in which a cooling tower with steam rising from it can clearly be seen, with the Syrian images, where no such structure appears.

Even told The Associated Press that another piece of evidence against the reactor theory was that satellite pictures of the Syrian installation taken since 2003 showed no sign of a plutonium separation facility, which prepares fuel for a nuclear reactor — typically a large structure with visible ventilation openings.

" It's very difficult to hide a separation plant," he said. "It's more difficult to hide a separation plant than to hide a nuclear reactor."

"In Yongbyon, the supposed sister facility in North Korea, you can see all those signs that I am pointing out that are missing in the Syrian place," Even added. "You can see the chimneys, you can see the ventilation, you can see the cooling towers, you can see the separation plant. All that is missing from this building in Syria."

Even believes the Syrian cleanup, in which large quantities of soil were bulldozed over the site, was an attempt to smother lethal radiation from a plutonium processing plant.

"Somebody made a lot of effort to bury deeply whatever remains of this facility," he told The AP. "Not just to hide it but to pile up a large mound of dirt on top of it."

Even said Syrian authorities might have taken similar cleanup action if the site had held chemical or biological weapons, but it would not have made sense for Israel to have taken the military and diplomatic risk of attacking such a facility, long a known part of Syria's arsenal.

"We know already that the Syrians have in place armed missiles with chemical weapons," he said. "They are already well-equipped in that department."