Tehran, Iran (CNN) -- The release of American hiker Sarah Shourd has been "canceled" because the judicial process has not been completed, a prosecutor said Friday, according to the semiofficial Iranian Labour News Agency.

Iranian officials had said Thursday that Shourd, one of three American hikers held in Iran for more than a year, would be released Saturday.

"The news [of the impending release] is not approved by the judiciary and, naturally, any decision regarding the defendants is contingent upon the completion of the due process," said Abas Jafari Dolatabadi, Tehran's public and revolutionary prosecutor, according to ILNA.

The Islamic Republic News Agency, an official agency of the Iranian government, cited the deputy director of the president's office of communications as saying that Shourd's release had only been "postponed."

"He said more details will be given later," it added.

Shourd, 32, along with Shane Bauer, 28, and Josh Fattal, 28, were detained July 31, 2009, after they allegedly strayed across an unmarked border into Iran while hiking in Iraq's Kurdistan region.

Tehran has said the three hikers were spies, and Iran's intelligence minister has hinted the country may consider releasing them in exchange for the release of Iranian prisoners, according to state news outlets.

Masoud Shafii, the Iranian lawyer who represents the hikers, said he has put in a formal request for the trio's release within the past two weeks. Shafii said he told prosecutors that a year had passed since their arrests and the government had not shown any just cause for their imprisonment, and that Shourd has a medical condition that requires proper care.

A spokeswoman for the families told CNN that Shourd told her mother during their sole visit, over two days in May, that she had found a lump in her breast.

The hikers' families' website, freethehikers.org, said Shourd has been in solitary confinement, able to meet for only two 30-minute periods per day with Bauer, who is her fiancé, and Fattal. The two men share a cell.

The three Americans -- all of them graduates of the University of California, Berkeley -- have not been charged, the website says. They are in Evin Prison in Tehran, have been able to telephone their families only once, on March 9, and have been denied access to their lawyer, the website adds.

"Shane, Sarah and Josh care greatly about our world and have a documented record as advocates for social and environmental justice," it says. "They admire and respect different cultures and religions and share a love of travel that has taken them to many countries. That is why they went to Kurdistan, not because they wanted to enter Iran.

"Their protracted detention without due process is illegal according to international and Iranian law and must end immediately. It is widely acknowledged that they are being held for political purposes that have nothing to do with the facts of their case. Their detention is arbitrary and inhumane and we call on the Iranian authorities to release them without further delay."

CNN's Shirzad Bozorgmehr in Tehran and Mary Snow in New York contributed to this story.