UPS plans to eliminate its day sorting operations at a Swan Island facility in Portland, putting 321 mostly part-time employees out of work, the company notified state officials on Wednesday.

The Atlanta-based shipping company told state officials that its Portland sorting facility will permanently end its daytime shift by April 19. The closure means that 272 part-time and 11 full-time employees, as well as 48 part-time and full-time managers, will lose their jobs.

The company said the closure was due to a decline in package volume.

“UPS will attempt to mitigate this loss by offering work to affected employees if other positions become available,” Lori Cruz, human resources business partner director at UPS, wrote to state labor officials. Cruz added that the layoffs impact both union and non-union workers.

During an earnings call in January, UPS said that it would lay off 12,000 workers, or roughly 2.5% of its workforce, as demand for package delivery services stagnates. CEO Carol Tome said that reducing the company’s workforce would save the company $1 billion this year.

The layoffs come just months after UPS averted a massive strike by agreeing to a new labor contract with the Teamsters union last summer.

Teamsters Local 162, which represents some of the workers at the Portland facility, notified members about the changes to its day sorting operations.