The Planned Industrial Expansion Authority on Thursday approved a 25-year property tax abatement for the $50 million conversion of the so-called “Flashcube Building” into 181 apartments.

Worcester Investments has a contract to buy the long-vacant office building at 720 Main St. for $5.7 million. The PIEA board approved its request for a 10-year, 100 percent property tax abatement followed by a 15-year, 50 percent abatement.

Charles Renner, a Husch Blackwell LLP attorney representing Worcester…