LYNN – A major residential developer’s tentative plan to purchase 14 Central Ave. is good news for downtown, city officials said Thursday.Alex Steinbergh, principal of RCG LLC, confirmed on Thursday that the Somerville-based development firm has placed the former school administration building “under agreement.”Steinbergh declined to discuss RCG’s prospective purchase of one of downtown’s largest vacant properties, but said firm representatives might discuss the agreement in greater detail later this week.The six-story, 47,000 square foot office building is valued at $1.4 million in city assessing records.Economic Development and Industrial Corporation Director James Cowdell said city planners are “keeping our fingers crossed” regarding RCG’s interest in 14 Central Ave. Cowdell credits RCG with doing a good job converting the Sloan manufacturing building opposite District Court into residences and the Franklin Street fire station into condominiums.”I’m excited because RCG has a good track record. Everything they’ve touched has come out good,” he said, adding city officials will “sit down immediately to talk about plans” for 14 Central Ave. if RCG makes a commitment to buy the building.Mayor Judith Flanagan Kennedy said RCG is one of “several interested parties” looking into buying 14 Central. She declined to name other potential buyers on Thursday but said one developer might be interested in combining the 14 Central purchase with the acquisition of Anthony’s Hawthorne.Cowdell has described 14 Central as a “linchpin” to downtown development.He wants to see 14 Central developed for residential and commercial use with parking for tenants located on the Anthony’s Hawthorne site bound by Willow, Washington and Oxford streets. Cowdell said a development plan encompassing Anthony’s and 14 Central, along with the former site of American Byproducts on Andrew Street, could attract several developers to downtown to replicate projects similar to RCG’s Sloan lofts.Cowdell said city visions for 14 Central’s development include providing space on its ground floor for businesses with residences on the upper floors.The building has been empty for nearly seven years after the School Department moved its office to 90 Commercial St.The city lists its owner as M & P Partners Limited Partnership. A November auction failed to attract bidders interested in meeting a $499,000 bid minimum for the property.School officials hired air testing firms to check the building in 2002 after over 30 school workers complained about respiratory problems. The employees subsequently returned to work but school administrators eventually moved their offices to the Lynn Vocational Technical Institute annex on Commercial Street.A Needham firm found no signs of “sick building” syndrome that caused problems for the School Department when it occupied the modern, multi-story structure eight years ago.The Athanas family is interested in working with the city to draft a development plan for the Hawthorne site, a family spokesman said in November. But Wig Zamore said environmental assessments need to be done around the Hawthorne property to determine underground contamination levels from locations including the former Whyte’s Laundry next to the Willow Street post office.