Cairo, Egypt (CNN) -- Egypt is putting the judicial heat on deposed President Mohamed Morsy and the political wing of the Muslim Brotherhood, the Islamist group that dominated his government.
Prosecutors are investigating complaints against the former democratically elected president over accusations of spying and killing protesters and have frozen the assets of more than a dozen people in a probe of violence in Cairo.
The developments come as authorities began choosing an interim government and take steps to form a new civilian government, after the military overthrew the Morsy administration in a coup.
Deputy Prosecutor General Adel al-Said.said the killing-spying probe started after complaints surfaced against Morsy and several leaders of the Brotherhood's Freedom and Justice Party.
The accused "committed crimes of spying (communicating) with foreign entities with the intent of harming national interest," the complaints say.
They cite the killing of "peaceful protesters and incitement thereof, acquiring weapons and explosives, attacking military barracks and harming the safety of the nation, its lands and its unity, as well as causing serious damage to the economy through the use of power and terrorism."
A judicial source has told state-run news agency MENA that investigators looking into the complaints have not questioned Morsy. Morsy's whereabouts are unknown, but he is thought to be in custody.
In another move, prosecutors ordered the freezing of the assets of at least 14 people as part of an investigation into violence in several areas of Cairo, the state-run news agency MENA said.
The people include several members of the Muslim Brotherhood and hard-line militants from the Salafist and Jamaa Islamiya movements.
MENA says the people include Muslim Brotherhood Supreme Guide Mohamed Badei, a spiritual leader; his deputy Khairat al-Shater; and deputy head of the Freedom and Justice party Essam el-Erian.
Others include former Supreme Guide Mohammed Akef and Mohamed Beltagi, a former Muslim Brotherhood lawmaker.
Morsy and his party were ousted in a military coup on July 3.
On Friday, U.S. State Department spokeswoman Jen Psaki said she agreed with the German foreign minister's call for Morsy to be released.
Psaki said the detentions of Morsy and members of the Muslim Brotherhood were "politically motivated" and urged the military to let them go.
"It is, of course, up to the Egyptian people, as we've said a number of times, to determine their future and the path forward," she said. "We are working with the interim government, and we -- and I can also confirm for you that Ambassador Patterson has met with the interim president, as well."
Anne Patterson is the U.S. ambassador to Egypt.
Though Morsy was elected president a year ago, Psaki said, "it's about more than what happens at the ballot box. Most democratic transitions take years to take root and stabilize, especially following decades of autocratic rule. And what we're focused on now is continuing to encourage that process to move forward by including all sides."
Asked about the administration's failure to describe the ouster as a coup, Psaki said, "We have not defined it yet. We are taking the time to evaluate and continue to do that."
Identifying Morsy's forced removal from office by the military as a coup could require the United States to suspend its $1.3 billion in annual military aid to the country, which has been a strong U.S. ally in the Middle East.
Sen. John McCain, R-Arizona, has called for such a move.
Tens of thousands of people rallied Friday in front of a Cairo mosque, calling not only for Morsy's release but for his restoration to the job of president. The crowd had thinned Saturday as supporters erected tents and appeared to be settling in for a long stay.
Fifty-one people died there Monday when protesters clashed with security forces who opened fire.
Many of Morsy's supporters have vowed they will risk their lives to see him back in power.
Those backing his overthrow have been unpersuaded.
A Pentagon source said Thursday that the White House planned to deliver four F-16 fighters to Egypt but was reviewing its military aid arrangements.
CNN's Schams Elwazer reported from Cairo, Tom Watkins reported from Atlanta and Mike Martinez reported from Los Angeles. CNN's Joe Sterling contributed to this report