"Obviously, we're very pleased with it. Obviously, we are hoping that this will lead to substantial additional information on al Qaida, on al Qaida's plans and al Qaida's operations," White House press secretary Ari Fleischer told reporters during an afternoon briefing.
President George W. Bush expressed his appreciation to the Pakistani government for its efforts in capturing Mohammad.
Mohammed was arrested before dawn Saturday during a raid on an Islamabad apartment, officials said. A Pakistani newspaper, The News International, reported that Mohammad was caught sleeping and offered no resistance when he was taken into custody.
Pakistan authorities told the newspaper that Mohammad was carrying names and phone numbers of al Qaida sleeper cells in North America.
Mohammad, 37, was indicted in 1996 for his alleged involvement in a conspiracy to bomb U.S. airlines flying routes to the United States from Southeast Asia. Mohammed has also been listed on the FBI's most-wanted list.
The U.S. Department of State had offered a $25 million reward for information leading to his capture.
U.S. officials considered Mohammed one of al Qaida's key planners and the mastermind behind the plan to place 19 hijackers aboard four commercial aircraft and use them as fuel-laden guided missiles.
The hijackers crashed three of those airliners into the World Trade Center and the Pentagon. Some 3,000 people were killed.
Mohammad is considered one of Osama bin Laden's top lieutenants. Bin Laden, a Saudi fugitive, is also wanted by U.S. officials as the leader of al Qaida and his involvement in the Sept. 11 attacks.
U.S. officials won't confirm the exact whereabouts of Mohammad. Pakistan security officials said that the U.S. and Pakistan governments had agreed not to discuss the suspect's whereabouts until the investigation was complete.
Eugene R. Fidell, the president of the National Institute of Military Justice, said that Mohammad is likely in the hands of the military or the CIA, and if he is in U.S. custody, it is unlikely that he would be brought to the United States.
Fidell said bringing the suspect to United States could open up the possibility that a federal judge would want to review his detention, something intelligence officials would consider an intrusion.
"He could be in Pakistan, Afghanistan, on a ship -- though they are not supposed to keep (prisoners of war) on a ship," Fidell said. Mohammad could also be held at any number of military bases set up in the region where he was caught.
How long the government holds him depends, Fidell said, on how difficult it is to extract information from him.
Asked how much pressure Bush believed should be placed on Mohammad during the interrogation process, Fleischer said the "standard for any type of interrogation of somebody in American custody is to be humane and to follow all international laws and accords dealing with this type of subject. That is precisely what has been happening and exactly what will happen."
It is also unclear whether Mohammed would face a trial in the United States or a military tribunal set up shortly after Sept. 11, 2001, to try suspects linked with the terrorist attacks.
Fleischer said any such decisions would be made by Bush.