NEW YORK/TOKYO, Sept 30 (Reuters) - Hedge fund Elliott Management said it owns a "significant" stake in troubled Japanese industrial conglomerate Toshiba Corp (6502.T), which is conducting a strategic review amid pressure from other investors that could include a sale of the company. Elliott, one of the world"s most powerful activist investors, which oversees some $48 billion in assets, has been invested in Toshiba since 2017 but recently increased its holding to just under 5%, making it a top 10 investor, people familiar with the firm"s investments said. The New York-based firm"s announcement comes just months after Effissimo Capital Management, Farallon Capital Management and other shareholders ousted Toshiba"s chairman after the company was found to have colluded with the Japanese government to put pressure on foreign investors. "Our investment in Toshiba reflects our strong conviction in the company"s underlying value," Elliott, which prefers to conduct its negotiations out of the public spotlight, said in the statement. The company is expected to update investors on its plans in the next weeks and is scheduled to release earnings in November. As those deadlines approach, Toshiba has told shareholders that it is mulling over three possible ways to try and unlock value, the sources said. Elliott has engaged with management and the board and said in a statement the firm has been "encouraged by the constructive nature of our engagement with the company in recent months." A Toshiba spokesperson said the company does not disclose communications with its shareholders. In its discussions, the sources said Elliott has suggested to Toshiba that the company"s stock could be worth 6,000 yen, which would mark a 27% increase from Thursday"s close of 4,715 yen. Shares of Toshiba rose more than 4% in Tokyo early Friday following the news, which was first reported by the Financial Times. The three possible approaches for Toshiba could include an outright sale to a private equity firm, a breakup of the company led by its management team or a combination of the two options, the sources said. Current shareholder frustration with the company might make a management-led breakup very unlikely suggesting instead that a private equity firm will play a role either as an outright buyer or a large minority investor, the sources said. Toshiba launched a full review of its current assets after dismissing in April a $20 billion takeover bid from CVC Capital Partners. The results of the review will be presented when the company announces a new mid-term business plan in October. read more . Since then Toshiba has been in talks with financial and strategic investors, including U.S. private equity firm KKR & Co Inc (KKR.N), to seek their ideas for a new strategy. read more Japan has recently become a popular hunting ground for U.S. activist investors, with Third Point targeting Sony Group (6758.T) and Olympus (7733.T) appointing three foreign directors after ValueAct took a stake in the company. ValueAct has also invested in Nintendo (7974.T) and Seven & i Holdings (3382.T). Elliott too has previously engaged in Japan when it built a nearly $3 billion stake in SoftBank in early 2020. While it trimmed the stake as the stock price climbed, the hedge fund remains invested in SoftBank. During the first half of 2021, 10 campaigns were launched at Japanese companies, data from investment bank Lazard shows.