CAIRO - Investigators began questioning Egypt's ousted president Mohamed Morsi and members of his Muslim Brotherhood on Sunday over their escape from jail during the 2011 uprising, judicial sources told AFP.

Prominent liberal leader Mohamed ElBaradei, who assisted in the talks Beblawi began a day earlier with ministerial candidates, was sworn in as interim vice president for foreign relations, the presidency said. Sunday's inquiry relates to the escape by Morsi and dozens of Brotherhood members from Wadi Natrun prison during the uprising that ended former president Hosni Mubarak's three-decade rule.

Egypt’s public prosecutor on Sunday ordered the freezing of assets belonging to 14 top Islamists, as the US dispatched its first senior official to Cairo since president Mohamed Morsi’s ouster.

US Under Secretary of State Bill Burns will visit Egypt from Sunday to Tuesday, the State Department said, adding he would “underscore US support for the Egyptian people”. His trip comes amid growing pressure on Morsi’s Muslim Brotherhood, which is in disarray with key figures either detained, on the run or keeping a low profile. It also comes amid international calls for the release of the detained Morsi, Egypt’s first freely elected president who was topped in a popularly backed military coup on July 3.

The Brotherhood has refused to join the new government headed by caretaker prime minister Hazem al-Beblawi who is pushing ahead with talks on forming his cabinet.

On Sunday, Beblawi appointed former ambassador to Washington, Nabil Fahmy, 62, as foreign minister, while prominent liberal leader Mohamed ElBaradei, 71, was sworn in as interim vice president for foreign relations.

Beblawi has said his cabinet’s priorities would be to restore security, ensure the flow of goods and services and prepare for parliamentary and presidential elections.

The asset freeze is part of an investigation ordered by public prosecutor Hisham Barakat which affects nine Muslim Brotherhood leaders, including the group’s general guide Mohamed Badie, and five Islamists from other groups including ex-militant faction Gamaa Islamiya, judicial sources said. It relates to four deadly incidents since Morsi’s overthrow, including clashes in Cairo last Monday in which dozens of people died.

The order comes a day after prosecutors received criminal complaints against Morsi, Badie and other senior Islamists, with a view to launching a formal investigation.

The complaints include spying, incitement to violence and damaging the economy, although the prosecutor’s office did not say who made the allegations.

Morsi has not been seen in public since his ouster. In his first public comments since removing the Islamist leader, military chief General Abdel Fattah al-Sisi said the army’s leaders made the move after urging Morsi to hold a referendum on his presidency, which he rejected.

“The armed forces, with all its personnel and its leaders, decided without reserve to be at the service of its people and to empower their free will,” he said in a statement.

In Brussels, EU foreign policy chief Catherine Ashton said the 28-member bloc was following developments in Egypt with “deep concern”, while also calling for prompt elections and deploring recent violence.

Interim president Adly Mansour had set a timetable for elections by early next year, according to a roadmap drafted by the military, while Beblawi’s new cabinet could be unveiled by Tuesday or Wednesday.

During his single year of turbulent rule, Morsi was accused of concentrating power in Brotherhood hands, sending the economy into free fall and failing to protect minorities.

But his supporters say his overthrow was a military coup and an affront to democracy, and are planning more mass protests on Monday.

Demonstrators will march to the Republican Guard headquarters, Brotherhood spokesman Tareq al-Morsi told AFP.

Rival protests are also planned on Monday in Tahrir Square and at the Ittihadiya presidential palace by the main coalition that had called for Morsi’s resignation.