A senior U.S. official said Tuesday that at least one of Al Qaeda's suspected biological and chemical weapons production sites is now in the hands of "the good guys" and is being examined to determine the extent of the terror network's capabilities.

The site, near Mazar-e-Sharif, fell into the hands of the Northern Alliance when the anti-Taliban rebels took control of the city last weekend, the official said. The fate of one other site near Kabul is unknown at this point, the official said, and at least one more near Durunta is still in Taliban hands.

Over the weekend, Secretary of Defense Donald Rumsfeld said U.S. forces have bombed some of the sites in Afghanistan that could have been involved in producing weapons of mass destruction. Others, however, were left unscathed.

Officials opted not to bomb some, the official told Fox News, because of the contamination danger it might pose to surrounding areas and so forensics experts could examine the sites.

"If you're trying to find out what they're doing and what they have, it's better to inspect it than to destroy it," the official said. "You can do a lot more with a swab than with a 500-pound bomb."

U.S. officials have said they believe Al Qaeda has access to crude chemical weapons such as chlorine and phosgene poison gases.

But they said it is unlikely that Usama bin Laden's network has more complex weapons such as sarin or nuclear weapons. They have also expressed concern that the group may have radiological weapons — mixtures of conventional explosives and nuclear material designed to spread radiation without a nuclear detonation.

Rumsfeld has echoed the comments of President Bush, who has repeatedly stated that he believes Al Qaeda would use any chemical, biological, radiological or nuclear weapons it has. "They are not worried about loss of life," Rumsfeld said.

Jim Angle currently serves as chief national correspondent for Fox News Channel (FNC). He joined FNC in 1996 as a senior White House correspondent.