Egyptian journalist, researcher, and Sinai expert Ismail Alexandrani was arrested at Hurghada Airport Sunday afternoon, though the charges against him have not been revealed, his wife announced on Twitter on Monday.

A source told Ahram's Arabic website that prosecutors had issued a warrant for Alexandrani's arrest, and that he was referred to State Security prosecutors for questioning.

Late Sunday, friends of Alexandrani had reported on social media his detention at Hurghada Airport Sunday afternoon where he was questioned for over 19 hours.

Security officials reportedly first told the detained journalist's friends it was only a "chat" and that investigation started late because the officer who was questioning him had an inspection patrol for security procedures at the airport.

Security officials had also reportedly assured his friends he would be freed.

Political science professor and activist Rabab El-Mahdy announced on her Facebook page that she received a call from Alexandrani, who informed her that he was going to be investigated by Cairo's State Security prosecution.

She added that former presidential candidate and human rights activist Khaled Ali was going to attend the interrogation with him.

The journalist was coming to Egypt from Germany to visit his sick mother, Sakr wrote, adding that Alexandrani last got in contact with him after security authorities took his passport, after which his phone was turned off.

Alexandrani, 32, is a sociopolitical researcher and investigative freelance journalist who specialises in Sinai affairs.

He last published in 2015 a chapter called "Violence in Sinai: the State's War on Society and Producing Terrorism" in a book titled "L'Egypte en revolution(s)" (Egypt in revolution[s]).

He is also a volunteer researcher responsible for Sinai issues at the Egyptian Centre for Economic and Social Rights (ECESR).

Alexandrani has been a Fellow Researcher at the Paris-based Arab Reform Initiative (ARI) since 2013, where he studies "the future relationship between the progressive Islamists and the Secular Left in Egypt."

He was a Visiting Arab Journalist Fellow at the Woodrow Wilson Center (February-May 2015) and won the Open Eye-Hany Darweesh Award for Exceptional Essay in Germany in 2014.