Park lost her immunity as of Friday, after the court upheld her impeachment by the National Assembly.

"We have not yet delivered a summons to Park," a prosecution source said, asking not to be named. "We have not made any decision on anything."

Prosecutor-General Kim Soo-nam is known to be listening to various opinions from senior prosecutors and elders in the legal circle.

There has been speculation that the prosecution could delay the investigation until after the upcoming presidential election which will likely take place in May.

Still, considering that the trials of major figures embroiled in the scandal, such as Park's friend Choi Soon-sil and Samsung Group's de facto leader Lee Jae-yong, are underway, the prosecution may seek to speed up its investigation of the former president, experts say.

They said that Park can be summoned as early as this week, if prosecutors are determined to conclude her questioning and indictment by the end of March or early April.

Prosecutors have been reviewing the investigative materials over the scandal handed over from an independent counsel team, led by Park Young-soo. Park's team wrapped up its probe last month, after putting 30 suspects on trial.

The special counsel team had unsuccessfully sought to hold a face-to-face interrogation of Park at the presidential office.

A protracted legal battle is expected down the road as the president has denied all criminal charges leveled against her.

In a statement released after she left the presidential office Cheong Wa Dae on Sunday, Park Geun-hye said "the truth will certainly be unearthed someday, though it will take time." (Yonhap)