Lee Jae-yong, the imprisoned de facto leader of Samsung Group, is under police investigation over an allegation that he illegally took propofol shots.

The Gyeonggi Nambu Provincial Police Agency said on Wednesday that they are looking into the allegation that the vice chairman of Samsung Electronics illegally used the anesthesia drug at a plastic surgery clinic in Seoul last year.

The police reportedly visited Lee at the Seoul Detention Center in Uiwang last month to take a hair sample for drug testing.

Lee is currently serving a two-and-a-half-year prison term for bribing impeached former President Park Geun-hye and her longtime friend Choi Soon-sil to win government support for a smooth father-to-son power transition at Samsung.

Samsung Electronics denied the allegation, saying Lee has never illegally been administered the drug and only took it for medical purposes.

This is the second time that Lee is suspected of illegal propofol use after the Anti-Corruption and Civil Rights Commission made similar accusations early last year.

Lee at the time requested that the case be reviewed by an independent committee consisting of outside experts to see whether the prosecution's investigation was legitimate.

A decision on convening the committee is expected to be made by a citizens’ panel on Thursday.