Two Senate committees want to investigate whether U.S. intelligence accurately pointed to banned weapons in Iraq as claimed by the Bush administration in going to war, senators said Sunday.

More than 11 weeks have passed without conclusive evidence of an Iraqi program to develop weapons of mass destruction, senators said, and it's time to investigate whether intelligence reports saying so were correct.

An investigation doesn't mean senators think that something was done incorrectly, Sen. John Warner (search), R-Va., chairman of the Armed Services Committee (search), said in a televised interview.

"By the fact that we're just investigating it, should not in any way indicate that we're putting any credibility doubt against" the CIA (search) or the Bush administration, Warner said.

He said his committee and the Senate Intelligence Committee might look jointly into the situation.

One member of the Intelligence panel, Sen. Bob Graham, running for the Democratic presidential nomination from Florida, went further than other senators in declaring in a televised interview that the government might have willfully distributed erroneous information on Iraq's arsenal.

"If we don't find these weapons of mass destruction, it will represent a serious intelligence failure or the manipulation of that intelligence to keep the American people in the dark," Graham said.

The Bush administration's main argument for the Iraq invasion was that deposed President Saddam Hussein held chemical and biological weapons and possibly was developing nuclear weapons. All were banned to Iraq under sanctions imposed by the United Nations after in August 1990 after Iraq invaded neighboring Kuwait and by subsequent U.N. resolutions.

Bush faced the question again Sunday in a news conference at St. Petersburg, Russia, as he ended an official visit. He seemed to have told a Polish television reporter Thursday that U.S. searchers had found weapons in the form of two mobile laboratories that the Americans say were to manufacture biological weapons.

"We've discovered weapons systems, biological labs, that Iraq denied she had, and labs that were prohibited under the U.N. resolutions," Bush said.

While Democrats have been bashing the White House for the military's failure to find unconventional weapons in Iraq, Warner and other Republican senators joined in Sunday in proposing a congressional inquiry.

"Absolutely, absolutely, there should be," said Sen. John McCain, R-Ariz., on ABC's This Week. "And I would think that the Congress is very well suited for that, a bipartisan committee, or Intelligence Committee report."

Warner said he and Intelligence Chairman Pat Roberts, R-Kan., have talked about a joint hearing into the intelligence about Iraq that the Bush administration was given.

CIA Director George Tenet "assured me that he's going to supply the Congress first and foremost with all the statements made by the administration on weapons of mass destruction and the underlying intelligence that supported those statements," Warner said.

Warner gave no time for an investigation.

The Pentagon is sending a new group of weapons hunters to Iraq to expand the search for banned weapons, beginning Monday.

Tenet defended his agency's work. "The integrity of our process was maintained throughout, and any suggestion to the contrary is simply wrong," he said Friday.

Intelligence mistakes might have been made, Sen. Evan Bayh, D-Ind., said, but he isn't ready to say information was manipulated.

"I don't think we know enough yet to cross the line, though, and start questioning motives and saying that people were consciously manipulating the facts," Bayh said in a televised interview.

It's important to find out what happened, though, said Sen. Joseph Biden, D-Del., ranking Democrat on the Senate Foreign Relations Committee.

"I think it cannot go uninvestigated, because big nations have two things: they have their word and they have their credibility," Biden said on CBS's Face the Nation.

"Our credibility is going to be called into question in other parts of the world" if nothing is found, he said.