South Korea's National Assembly started the third round of hearings on the corruption scandal involving President Park Geun-hye on Wednesday, this time focusing on her alleged inaction at the time of a deadly ferry disaster on April 16, 2014.

Of the 16 figures summoned, 13 appeared before the special committee, including her former aides and medical experts, who will be questioned about allegations she neglected her duties during the "the missing seven hours."

The presidential office argued that Park was updated with written reports on that day but has yet to say what exactly the president was doing. Rumors have spread that Park received medical treatment, as well as hair services, during the critical hours. 

Park was impeached last week by the National Assembly. Her failure to fulfill her constitutional duty as president to protect the lives of the people was cited as a major reason for the impeachment.

The witnesses present at the latest hearing session included Kim Young-jae and Cha Kwang-yul, who head hospitals regularly visited by Park's friend Choi Soon-sil, a key suspect in the scandal, and a nurse officer with the Presidential Security Service.

Three key figures, including nurse officer Cho Yeo-ok, however, did not show up, citing personal reasons. Cho, who currently resides in the United States, is likely to appear at the National Assembly next week, the defense ministry said.

The parliament issued orders of accompaniment for the remaining two witnesses, both presidential officials. The order is issued to forcefully make a suspect or witness appear at a hearing when he or she refuses to attend without a justifiable reason.

The committee also said it will conduct an on-site investigation into the presidential security office on Friday.

The presidential office, however, rejected the plan, citing concerns about the possible leak of confidential information.

During the two previous sessions last week, the parliament committee questioned business tycoons and Park's confidante Choi Soon-sil's key acquaintances. (Yonhap)