Rite Aid and the grocer Albertsons called off an agreement to become a single company with the deal facing shaky prospects in a shareholder vote.

Shares of the drugstore chain plunged after markets opened Thursday.

The owner of Safeway and other grocery brands had announced in February plans to buy Rite Aid's more than 2,500 stores with the goal of becoming "a leader in food, health and wellness." But a major shareholder and two proxy advisory firms came out against the deal.

Rite Aid Chairman and CEO John Standley said in a prepared statement late Wednesday that after hearing the views of shareholders, the drugstore chain is "committed to moving forward and executing our strategic plan as a (stand-alone) company."

Rite Aid also said its board will consider governance changes, although it did not elaborate.

The company cancelled a shareholder meeting to vote on the deal that had been scheduled for Thursday. Both businesses said neither party will be responsible for any payments due to the deal's termination.

Privately held Albertsons Companies, based in Boise, Idaho, was offering either a share of its stock and $1.83 in cash or slightly more than one Albertsons share for every 10 Rite Aid shares.

One of Rite Aid's biggest shareholders, Highfields Capital Management, said that deal was "in the best interests of Albertsons and Rite Aid management, but not Rite Aid shareholders." The investment firm said in June that it would vote its roughly 47 million shares against the deal.

Two prominent shareholder advisory firms — Glass Lewis & Co. and Institutional Shareholder Services — also recommended no votes. Glass Lewis said the deal was "not critical to Rite Aid's viability" and provided no meaningful premium to investors.

ISS, meanwhile, said it was concerned that the deal would introduce a new set of risks from the grocery business.

Rite Aid, based in Camp Hill, Pennsylvania, has remodeled many of its stores to expand pharmacy services and offer more health products. It also has a pharmacy benefit management business to bring in customers.

But it will face significant challenges continuing as a stand-alone company. The drugstore chain has struggled with high debt levels and tough competition, as narrowing drugstore networks have pushed customers away from its stores.

The company has neither "the scale nor the balance sheet to compete with much larger and well capitalized rivals like CVS and Walgreens," Moody's Vice President Mickey Chadha said in an email.

Earlier this week, Rite Aid said it was chopping its fiscal 2019 forecast because generic drug pricing wasn't shaping up how it expected in April, when it first laid out expectations.

The nation's largest drugstore chain, Walgreens, tried unsuccessfully to buy all of Rite Aid last year but scuttled that deal after encountering regulatory resistance. Last September, Walgreens Boots Alliance Inc. announced a slimmer agreement to buy nearly 2,000 Rite Aid locations and some distribution centers for about $4.38 billion.

Rite Aid had told shareholders last month that the Albertsons deal would help build scale and diversify as the company deals with increased competition and pressure on drug reimbursement rates.

Shares of Rite Aid fell nearly 12 percent to $1.53 at the opening bell, it's worst sell-off in a year.

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Follow Tom Murphy on Twitter: @thpmurphy