Solo Cup Co. announced Tuesday that it will close its manufacturing plant in Owings Mills in 2012, throwing 540 people out of work.

The company is putting the facility on the market prior to its scheduled shutdown date in March 2012, but production will continue there until that time. The 540 job cuts come from the manufacturing side of the operation while 120 employees in the corporate office will not be affected by the closing.

News of the plant closure rankled David Iannucci, Baltimore County’s director of economic development, who said the company had resisted efforts to work out a plan to keep the facility from closing.

Iannucci said he sent a letter to Solo in April, expressing the county’s support and requesting information about potential plant closures. He said he never received a response.

The county had a much stronger relationship with the company before Solo bought out Sweetheart Cup Co. in 2004, he said.

“It is very disappointing news and most unwelcome,” Iannucci said. “We have been dealing for the last two or three years with a series of rumors and commentary and buzz in the community on what’s going on at Solo and we’ve repeatedly tried to get inside the company and find out what’s going on there. But candidly, they have not been open.”

Solo Cup spokeswoman Angie Chaplin Gorman said the decision to close the facility was not tied to geography or dissatisfaction with the work force. Instead, a companywide review of operations found the Owings Mills plant had aging equipment and excess capacity.

“This decision didn’t have anything to do with the business community here,” she said. “It was us looking at manufacturing capacity across our network. Our employees here have been strong performers and that is not the reason why this facility was chosen.”

The company also announced plans Monday to shutter its North Andover, Mass. and Springfield, Mo. plants, leading to cuts of 360 and 340 jobs, respectively.

The Owings Mills plant, which manufactures items including paper and plastic cups and plastic cutlery, will see that work transferred to facilities in Illinois, Georgia and Texas.

Solo’s 508-employee manufacturing facility in Federalsburg also will pick up some of the work and possibly some of the manufacturing employees from Owings Mills. A distribution center in Hampstead also will remain open.

The plant closure is the latest blow to Baltimore County’s manufacturing sector, which once made up a large portion of jobs there.

The county is home to the Sparrows Point steel mill, which, at one point under Bethlehem Steel ownership, employed 36,000 people. The mill, now owned by the Russian company Severstal has about 2,500 workers according to the United Steelworkers union.

On Friday, The Baltimore Sun reported that the mill would be idled around July 1 for 30 days due to weak demand. In doing so, the company could lay off as many as 600 workers temporarily, the newspaper said.

Baltimore County has been hit hard by other recent job losses, including 250 planned cuts from Black & Decker’s merger with The Stanley Works and Legg Mason Inc.’s recent announcement that it would eliminate 250 jobs at its Owings Mills location over the next 18 months.

But Iannuci pointed to Monday’s announcement from Middle River Aviation Systems that it plans to add 200 high-tech manufacturing jobs to its Middle River facility.

“This is a very big disappointment and for the individuals it’s tragic news,” he said of the Solo announcement. “But in a county of 800,000 people we will move on.”

Anirban Basu, chairman and CEO of Sage Policy Group in Baltimore, said the Solo plant closure is part of “a pattern of corporate departures from Maryland.”

“During uncertain economic times, one of the features of economic life is that businesses look to pare down their cost structures,” Basu said. “If businesses come to believe that the cost of doing business in Maryland is too high, then the predictable response is that they’ll reduce their presence in Maryland, and this may be some of what has happened.”

Basu said the state needs to assess how competitive it is in attracting and retaining businesses to reduce that trend, one that he said could be masked by increased federal spending on military and intelligence facilities in the state.

“That will give us a false sense of security regarding our competitiveness for private industry,” he said. “Whether it’s BP Solar or Solo Cup or Legg Mason or Northrop Grumman or General Dynamics, Maryland needs to focus intensely on its business climate and what it can do to put it on par with leading states like Virginia and Texas.”

Richard Clinch, director of economic development at the University of Baltimore’s Jacob France Institute, said the new jobs building jet engine devices at Middle River Aviation’s plant are a win for the county, but they represent a shift in Maryland’s job market.

“It just goes to show you that Maryland’s strengths tend to be in higher value-added products,” he said. “We’re winning in things like General Dynamics. We’re losing like things in Solo Cup and Black & Decker.”

He said the loss of middle-wage jobs will be painful.

“What Maryland is headed for is a very bifurcated labor market where we have lots of jobs on the top and lots of jobs on the bottom, and it’s this hollowing-out of middle-class jobs that is hurting Maryland,” Clinch said.

Daily Record business writer Nicholas Sohr contributed to this article.