HARRISBURG, Pa. – The Hershey Co. is proposing to cut up to 600 jobs in a move to modernize and expand one of its hometown plants and turn the other — the original chocolate factory built by founder Milton Hershey — into an office building.

The plan, announced Tuesday, is part of a tentative agreement with union negotiators and must be approved by a majority of the approximately 1,600 members who work at both factories. A vote is set Friday.

Locals fear the nation’s second-largest candy maker is slowly but surely leaving the town built by Mr. Hershey. The 105-year-old plant at 19 E. Chocolate Ave. greets passers-by with the smell of chocolate, and streetlights in front of it are capped by giant metal models of Hershey’s Kisses. Corporate offices just won’t give the same feel.

“I’m quite sure he’s doing tailspins in his grave,” said Joyce Wolf, an assembly line worker at the plant whose mother also worked for the candy company.

But Wolf, 60, said she and others fear that if members of Chocolate Workers Local 464 reject the plan, even steeper job losses could result.

Hershey spokesman Kirk Saville said the move is necessary to remain competitive in an ever-changing global marketplace.

Saville said the newer West Hershey factory would become one of the world’s largest and most advanced chocolate plants, employing 1,100 people, up from about 500. If the union rejects the plan, the company is threatening to move the expansion and jobs elsewhere.

Hershey, which did not disclose its budget for the project, had more than 12,000 full-time employees worldwide at the beginning of this year and counted revenue of $5.3 billion in its most recent fiscal year.

The Chocolate Avenue plant’s unwieldy layout, low ceilings and narrow column spacing make it inefficient and troublesome to upgrade, Saville said.

The announcement comes a little more than three years after Hershey mounted a broader effort to expand overseas while slashing jobs and closing inefficient plants in North America.

Union officials did not return phone messages Tuesday. But they were briefing the rank-and-file on the deal, said Wolf. She said union members may have no choice but to ratify the pact.

“From what I understand, we were told if we vote no and against it, they’re not going to even consider doing anything over at West (Hershey) and we’ll all be out of a job,” Wolf said.