Amy's Kitchen, one of the nation's largest makers of natural frozen foods, is planning to build a second manufacturing plant in Santa Rosa that one day could employ an additional 800 workers.

The Petaluma-based company, which already has 1,000 workers in Sonoma County, is proposing the largest business expansion in the city in at least a decade, according to Santa Rosa officials.

The new plant's building and equipment would cost between $40 million and $50 million, company CEO and co-founder Andy Berliner said this week. He has looked at potential sites but has yet to select one.

The family-owned company also has enough land for such a plant at its sister facility near Medford, Ore., Berliner said, but "clearly our ideal and our preference is to be here."

Santa Rosa Mayor Scott Bartley and other city officials welcomed the news.

"That is exactly the kind of stuff we need to see in the city," Bartley said. "The city will do whatever we can to try and accommodate them."

Berliner revealed his expansion plans Monday during an interview on the company's 25th year in business. With him were his wife and co-founder, Rachel, and their 25-year-old daughter Amy, the company's namesake.

Amy's Kitchen produces vegetarian frozen entrees, canned soups and other convenience food products. It employs nearly 1,900 workers in Sonoma County and abroad.

The company projects sales of $380 million this year. Steady growth in its frozen food products has propelled it into the ranks of the nation's largest food processors.

The Berliners founded the company in 1988 and opened a plant in Santa Rosa in 1994. They built a second facility near Medford in 2006 and started a small plant in Corby, England in 2011.

The family made headlines last month when they announced plans to build their first Amy's Kitchen fast-food restaurant in Rohnert Park. The site is located near the casino resort under construction by the Federated Indians of Graton Rancheria.

While announcing the proposed expansion in Santa Rosa, Berliner confirmed Amy's Kitchen has dropped plans announced in 2011 to build a $63 million plant in Greenville, S.C. An official last month told the Associated Press that the company had shelved its plans for the South Carolina plant.

Amy's Kitchen decided to scuttle the plant in part because it lacked a supply system in South Carolina of farmers producing the right selection of organic or natural crops, Berliner said. The company will try to sell the land there.

While it did not proceed with the South Carolina expansion, the company has continued to grow rapidly. Every year, the company needs roughly 50,000 square feet of additional production space, Berliner said.

In the last two years, Amy's Kitchen has invested about $19 million in improvements and new warehouse space at the Oregon facility.

Berliner would prefer to build in Santa Rosa largely because the company's existing Sonoma County work force has more depth of experience than its labor force in Medford, he said. That difference could prove crucial to the success of a large expansion.

"We feel we could build the work force more easily," he said.

Amy's Kitchen production line workers earn $8.50 to $16 an hour, with skilled workers in other departments earning more. The company pays at least 80 percent of the cost of its employees' health care premiums and has its own health center, where workers and their families can be treated by a physician for $5.

Santa Rosa officials said they have yet to discuss the expansion plans with the company. But they were quick to applaud the proposal.

"Having one of Santa Rosa's most valuable businesses expand by 800 employees is just tremendous news for the community," said David Gouin, the city's director of economic development and housing.

Community Development Director Chuck Regalia said it has been at least 10 years since such a major business expansion occurred in the city.

"We'd be very glad to help them find a spot in Santa Rosa," Regalia said.

Expansions this size have been rare throughout the county. However, the sponsors of the Rohnert Park casino have said their business eventually will employ 1,500 people.

Berliner said the company plans to talk to city officials this month and would like to break ground on the new plant in about a year.