Shafiq, who narrowly lost a 2012 presidential bid against Mursi, joined several other lower-profile candidates who have also said they will run, though some say they believe they have no chance against Sisi.
Sahar Aziz, an associate professor of Law at Texas A&M University, said it was likely that there was some truth to Shafik's claim that he was barred from leaving the UAE. He was escorted from the airport by unidentified security men, according to airport officials.
"I had a meeting with Shafik an hour ago at one of the hotels in New Cairo and confirmed his health", Dina Adly wrote on Facebook on Sunday evening. It said his family had remained behind in the Emirates.
A relative of Shafiq's told AFP that "we have no information about him". They came and took him.
Shafiq's family and lawyer said Sunday they had lost contact with him after what they called his deportation from the United Arab Emirates to Cairo, days after announcing his intention to run for president of Egypt next year.
"Shafiq has publicly asked to go to Egypt and his wish will be met", a source in the Gulf close to the matter told Reuters.
According to information by sources at Cairo's International Airport, when Shafiq's plane landed almost 50 family members and his loyalists met him at the airport.
Amira Ahmed Shafik said in a voice recording sent to Bloomberg that her father was denied access to his lawyer and that they planned to sue the Egyptian authorities over his treatment.
Adly also said in her post that all lines of communication with Shafik had been shut down since Friday.
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An official source at the interior ministry said: "We do not know anything about Shafiq".
One Egyptian judicial source said on Saturday Shafiq did not face any criminal cases in Egypt.
May Shafik said on Friday he was preparing to depart, first for Europe and the United States before returning to Egypt to start his campaign.
"I was surprised to know that I am prevented from leaving the UAE, for reasons that I don't understand and I am not willing to understand", he said in his statement.
"I call on the UAE leaders to order the lifting of any restrictions on my ability to travel".
The UAE has been officially silent on Shafik's candidacy announcement. Sisi's supporters see him as key to stability following the upheaval that followed the 2011 Egyptian revolt that toppled president Hosni Mubarak.
Sisi as a military commander led the ousting of former president Mursi in 2013, before his own landslide election a year later.
But his government is fighting a stubborn Islamist militant insurgency in the Sinai region and has also enacted painful austerity reforms over the past year to revive the economy but that critics say have dented his popularity.