A special counsel team investigating former first lady Kim Keon-hee questioned Kim's mother and brother over allegations that the family received preferential treatment during an apartment construction project in Yangpyeong, Gyeonggi Province, a decade ago.

The team began grilling former first lady's mother, Choi Eun-soon, and brother, Kim Jin-woo, on Tuesday morning, in the team's first interrogation of Choi in the investigation and the third questioning of her son, who had previously appeared in July and September.

The investigation concerns whether the family avoided paying the legally required development fees on a housing project between 2011 and 2016 and received an improper deadline extension.

Prosecutors are also looking into whether evidence destruction, concealment and obstruction of an investigation occurred after suspicions arose that the former first lady had helped former National Education Commission chair Lee Bae-yong obtain her post in exchange for expensive gifts.

The team found a congratulatory card from Lee and the resumes of four police officers, which were outside the scope of their initial warrant, during a July raid linked to Choi—all of which were nowhere to be found when investigators returned with appropriate search authorization.