Bristol-Myers Squibb confirmed on Wednesday that activist hedge fund Starboard Value owns a 1 million-share stake in the company and said separately its $74 billion deal to acquire cancer drugmaker Celgene is "on track" to close during the third quarter.

Starboard's stake is just a fraction of Bristol-Myers Squibb's 1.63 billion shares outstanding, but the fund has filed with regulators for the ability to buy more shares. The fund also has held meetings with management, Bristol-Myers Squibb said.

Starboard has not publicly stated its stance on Bristol-Myers' acquisition of Celgene, but activists have in the past taken stakes in companies to scuttle deals. Reuters reported last week the hedge fund is gauging investor support for the Celgene deal.

Dow Jones reported Wednesday that Starboard is unhappy with the deal, citing a source familiar with the matter. It also said Bristol-Myers' fifth-largest shareholder, Dodge & Cox, is also unhappy with the deal, citing sources.

The news sent Celgene's stock down slightly, while Bristol-Myers dipped a half a percentage.

Starboard acquired its shares on Jan. 31, Bristol-Myers said, the same day its nomination window closed. The hedge fund has nominated for the Bristol-Myers board Starboard's CEO and co-founder, Jeffrey Smith, as well as John Leonard, James Tyree, Steven Shulman and Janet Vergis.

Bristol-Myers Squibb's annual shareholder meeting is not yet scheduled, but it will occur after its special meeting to vote on the Celgene acquisition on April 12. The planned date for the meeting remains unchanged, keeping the deal on track for its expected closure by the company's third quarter.

Analysts at BMO earlier this month said they believe the "probability of a third-party buyer for Bristol-Myers Squibb" before the April vote is "very low," adding that "we do not believe a potential activist can change that."

The Celgene deal is aimed at giving Bristol-Myers Squibb more cancer drugs at a time when its immuno-oncology portfolio struggles to keep up with rival Merck's. Bristol-Myers Squibb on Wednesday underlined the benefits it sees in the deal, citing increased scale and a broader pipeline in the near and long term. It said that Celgene expects six near-term product launches that present "more than $15 billion in revenue potential."

Starboard and Dodge did not immediately respond to requests for comment.