United Natural Foods Inc., a publicly traded distributor of natural and organic foods, plans to move its corporate headquarters and 150 employees next May from Dayville, Conn., to the American Locomotive Works development on Valley Street in Providence.

The company also plans to expand its Providence work force to 240 employees over the next three years, but keep its warehouse in Connecticut.

“Given the economic downturn, this is great news for Rhode Island,” said Saul Kaplan, executive director of the Rhode Island Economic Development Corporation.

Governor Carcieri is scheduled to announce United Natural’s relocation tomorrow. That’s the same day the Rhode Island Department of Labor and Training is scheduled to release its September unemployment report. In July, the state’s jobless rate was 8.5 percent, the highest in 15 years and the second-highest in the country, with 48,000 residents out of work. Employers shed 1,200 jobs in July.

“The relocation of [United Natural’s] corporate headquarters to Providence is expected to bring good, high-paying jobs to Rhode Island with more job-growth opportunity to follow in the months and years to come,” Carcieri said in a news release prepared for the announcement.

United Natural distributes more than 60,000 products to more than 17,000 customers nationwide, including supermarkets, natural-product superstores and independent retail operators. The company has annual sales of $3.3 billion and earnings of $48.5 million.

The company has been offered tax incentives at the state and municipal level, but the packages would require approvals by the Providence City Council and the General Assembly, sources said. The incentives are based, in part, on the number of jobs the company brings to the state and include a type of tax reduction. More details are expected at the announcement.

Providence Mayor David N. Cicilline said, “These are good jobs paying between $65,000 and $75,000 a year. … It’s very exciting for Providence, and it will be very exciting for that neighborhood. This is the kind of economic development that we’re trying to bring to the city.”

The company’s distribution facility, the third-largest warehouse of its type on the East Coast, will remain in Dayville.

The company has agreed to sign a 10-year lease for 53,000 square feet of space for executives and administrators at the ALCO site being developed by Struever Bros., Eccles & Rouse, according to Tom Dziki, vice president of sustainable development for United Natural.

The ALCO site is a mixed-use development that will contain up to 1.7 million square feet of commercial, retail and residential space on the edge of the Olneyville section of the city.

Dziki said the move has been in the works for several months, prompted by the company’s need for more space. He said the company is the nation’s largest distributor of natural and organic foods.

Dziki said the company considered other sites near Dayville and in Massachusetts and Rhode Island, before settling on Providence. He said the city’s renaissance, its colleges and universities and its proximity to Dayville all played roles in the selection.

The ALCO site is a “green” building, and is expected to be a Leadership in Energy and Environmental Design (LEED) certified project, which was another factor in its favor, he added.

“Rhode Island is the best spot,” Dziki said. “We love the building, the whole story of the building … and being close to the downtown, with all the things that are going on downtown. It’s a real renaissance. We just want to be a part of that.”

United Natural will be the 13th company whose stock trades on the major public exchanges to call Rhode Island its headquarters, joining companies such as CVS Caremark, Textron and Hasbro. Publicly traded companies call attention to their headquarters state and are sought after by economic development officials.

Stock in United Natural (UNFI:Nasdaq) closed yesterday at $19.88 a share, down $2.28 a share.

cdunn@projo.com