South Korea's special prosecutor is seeking an arrest warrant for Samsung heir apparent Lee Jae-yong, on bribery charges.
The case is linked to a scandal that led to the impeachment of the country's President Park Geung-hye.
Samsung is accused of giving donations to non-profit foundations operated by Choi Soon-sil, a friend of Ms Park, in exchange for government favours.
The donations were allegedly made as it sought political support for a merger.
Mr Lee, also known as Jay Y Lee, was questioned for more than 20 hours at the prosecutor's office in Seoul last week.
He is currently vice-chairman of Samsung Electronics, but since his father, Lee Kun-hee, suffered a heart attack in 2014, he is considered de facto boss of the entire Samsung Group conglomerate.
The news sent Samsung shares lower, with Samsung Electronics stocks down 2% by midday in Seoul, and parent firm Samsung C&T down 0.8%.
A spokesman for the special prosecutor's office acknowledged the arrest of Mr Lee could be damaging for one of South Korea's biggest business but said "while the country's economic conditions are important, upholding justice takes precedence".
The claims against Samsung centre on a controversial merger between the electronics giant's construction arm, Samsung C&T, and an affiliate firm, Cheil Industries.
Prosecutors allege that Samsung gave money to a company co-owned by Ms Choi and her daughter, in return for Ms Park's support for the deal.
At the parliamentary hearing in December, Samsung admitted giving a total of 20.4bn won (£16m; $17.46m) to the two foundations, but denied seeking favours.
During that hearing, Mr Lee also said the firm had made separate payments to help fund Ms Choi's daughter's equestrian career, including buying an $850,000 horse - something the Samsung executive says he regrets.
Earlier on Monday the special prosecutor indicted the country's National Pension Service (NPS) chairman Moon Hyung-pyo on charges of abuse of power and giving false testimony.
The NPS is the world's third-largest pension scheme and was a major shareholder in the two Samsung Group affiliates. It is claimed Mr Moon pressured the organisation to back the deal - something the NPS has denied.