Former Mauritanian president Mohamed Ould Abdel Aziz was released by police early Monday after undergoing week-long questioning over suspected embezzlement, his lawyer said.
"He has not been charged but his passport, which was taken on his arrest, has not been returned," said attorney Taghioullah Aida, adding that Aziz had also been banned from leaving Nouakchott, the capital.
Aziz, 63, seized power in 2008 and served two terms as president before being succeeded in August 2019 by Mohamed Ould Cheikh El Ghazouani, his former right-hand man and ex-defence minister.
Aziz had gone to the headquarters of the General Directorate for National Security (DSGN) on August 17 after police went to his home and asked him to cooperate with investigators.
He was released at around 1:30 am on Monday, Aida said.
The interest in Aziz stems from "major suspicions of maladministration and embezzlement of public assets", a security source told AFP last week.
Aziz has been kept at arm's length by Ghazouani since leaving power.
Little more than four months after he left office, parliament set up a commission of inquiry into his affairs.
Aziz failed to answer a call to testify before the commission in early July.
MPs then swiftly approved a law to set up a High Court of Justice that would be empowered to try presidents and ministers in cases of "high treason".
The parliamentary report was formally handed to prosecutors this month.
It was followed on August 9 by a government reshuffle that turfed out four former ministers whose names surfaced in the investigation, including ex-premier Ismail Ould Bedda Ould Cheikh Sidiya.
Among the issues probed by the commission, according to sources in parliament, were the handling of oil revenue, the sale of state property in the capital Nouakchott, the winding up of a publicly owned food supply company and the activities of a Chinese fishing company called Pully Hong Dong.
The new prime minister, Mohamed Ould Bilal, was a minister several times under former president Sidi Ould Cheikh Abdallahi, who was deposed in the coup led by Aziz.