SEOUL, Feb. 27 (Xinhua) -- South Korean Prime Minister Hwang Kyo-ahn, who is serving as acting president after the impeachment in December of President Park Geun-hye, on Monday rejected a request to extend investigation by special prosecutors into a scandal embroiling the impeached leader.

Hwang said in a statement read by his press secretary that past probes achieved a major goal of the independent counsel act as key suspects and relevant figures were already indicted or investigated enough to decide whether to indict.

He said state prosecutors will continue probe into the remaining suspicions, noting that if any shortage is found in investigation by the state prosecutors, a new independent counsel act can be enacted in the parliament.

Under the independent counsel act that was passed in the parliament, special prosecutors kicked off investigation into the corruption scandal that led to Park's impeachment.

Their probe can be extended for up to 30 days with the acting president's approval, but Hwang's rejection would force the special prosecutors to end their probe on Tuesday.

Samsung Electronics Vice Chairman Lee Jae-yong and Choi Soon-sil, President Park's longtime confidante who is at the center of the influence-peddling scandal, have been taken into custody for bribery charges.

However, suspicions on other conglomerates have yet to be investigated, while Choi's illegal wealth believed to be concealed overseas has yet to be sought. Choi's daughter, who is accused of having entered a prestigious college illegally, still stays abroad to avoid investigation.

President Park had vowed to accept face-to-face interrogation by special prosecutors as well as state prosecutors, but she managed to avoid them. Park has been identified as a criminal accomplice to Choi.

Hwang's rejection had been widely expected as he is one of closest aides to the impeached leader.

The ruling Liberty Korea Party positively responded to the acting president's decision, but four opposition parties bashed Hwang and his rejection. Four floor leaders of the parties would hold an emergency meeting later in the day to discuss countermeasures.

Choo Mi-ae, chairwoman of the biggest opposition Minjoo Party, told a party meeting that her party will take all available actions, including the proposal of a new independent counsel act, in response to what she described as the worst decision in constitutional history.

Concerns remain that investigation by state prosecutors could be politically influenced as the acting president and the prosecutor general, who was named by the impeached leader, can negatively affect future probes.