Opposition leader Lee Jae-myung returned home early Friday after more than 13 hours of questioning by prosecutors over suspicions surrounding a land development project in Seongnam, located just south of Seoul, during his previous term as the city's mayor.

Lee of the main opposition Democratic Party is facing allegations that he facilitated business favors for a private developer in connection with a property development project in Seongnam's Baekhyeon-dong district during his term as mayor in the mid-2010s.

The so-called Baekhyeon-dong scandal centers on allegations that the municipal government of Seongnam gave special treatment to the private developer, named Seongnam R&D PFV, in connection with the project to develop the former site of the Korea Food Research Institute in the district into apartment complexes between 2015 and 2016. The firm allegedly earned windfall profits of 318.5 billion won ($237.4 million) as a private partner of the project.

Lee emerged from the Seoul Central District Prosecutors Office shortly after midnight, about 13 hours after he presented himself before prosecutors for questioning.

About 10 Democratic Party lawmakers, including members of the party's supreme council Reps. Jung Chung-rai and Seo Young-kyo, and other supporters cheered as Lee waved his hand and gave them a thumbs-up.

"This is a matter that could not constitute a problem if objective facts were considered, but I cannot shake off the impression that prosecutors had a preset goal and tried to patch together facts and incidents accordingly," Lee told reporters.

Prosecutors plan to review whether to seek an arrest warrant for Lee in consideration of the gravity of the case and the outcome of the questioning. (Yonhap)