Authorities in Yemen have released on bail a 22-year-old female engineering student whose name and phone number were on the shipping documents for the two bombs sent to the United States.
A lawyer for Hanan Samawi told ABCNews.com that the young woman had returned home after being held and questioned over the last 24 hours.
The lawyer said Samawi's father had been instructed to have his daughter avoid news reporters.
A Yemeni official briefed on the investigation said the suspect "is not allowed to leave the country pending further questioning."
The official said the shipping agent who received the packages was called in to identify her and said Samawi "was not the person who signed the shipping manifesto."
The official said authorities now believe it is a case of "stolen identity by an individual who knew the detained suspect's full name, address and telephone number."
Her arrest had been trumpeted by the President of Yemen, Ali Abdullah Saleh, as evidence of its cooperation with the U.S. and others to combat terrorism.
But as her fellow students mounted a protest Sunday at a university, her lawyers questioned why anyone involved in the plot would use their real name and phone number to ship a bomb.
President Obama's top anti-terrorism advisor went on ABC News Sunday to warn that authorities are hunting for other packages like the ones containing powerful explosives that were found Friday on UPS and FedEx cargo jets bound for the United States.
"We can't presume that there are none others that are out there," John O. Brennan told ABC News This Week host Christiane Amanpour. "What we're trying to do right now is to work very closely with our partners overseas to identify all packages that left Yemen recently and to see whether or not there are any other suspicious packages out there."
Brennan said the U.S. was "very fortunate" to have received help from Saudi Arabia, and that the assistance "saved lives here."
"Once they received the information, they contacted us immediately, and it was a race against the clock to find those packages, to neutralize them," he said. "And so we owe a debt of gratitude to the Saudis. I think their actions really saved lives here."
The administration's decision to publicly identify the Saudis as the source of that critical tip has brought some criticism, though, from Republicans on Capitol Hill. The ranking Republican on the Senate Intelligence Committee told ABC News Sunday that the White House was "stupid" to identify Saudi Arabia as the source of the tip that helped foil the Yemen-based terror plot to sent bombs to the United States by UPS and FedEx.
"Why do you finger the Saudis?" Sen. Kit Bond of Missouri said Sunday. "When you identify your sources, you may make it easier for Al Qaeda to retaliate. And you may embarrass the Saudis."