A lender seized the troubled office building at 31 Milk St. in Boston at auction today, marking the latest twist in the unraveling of Kambiz Shahbazi’s commercial real estate empire.

LNR Partners, the special servicer on the building’s securitized mortgage, took the 90,000-square-foot building back with a bid of $8.2 million.

Several dozen onlookers watched the auction unfold, and a pair of would-be buyers – a user-buyer and Boston’s Synergy Investment & Development – bid the property up from $5 million to $8 million. That price wasn’t close to the $16.1 million securitized mortgage on the property, though, so the lender took the property back.

It was not immediately clear whether LNR will unload the building quickly, or whether the servicer will engage a brokerage to fill up vacant office space before putting the property back on the market.

Shahbazi purchased 31 Milk St. in 2005, paying Paradigm Properties more than $19 million for the 11-story Class B office building. Shahbazi’s firm then chopped the property up into an office condominium and a retail condominium, selling the retail portion to the RAM Cos. for $3.75 million.

The downtown office building was part of a seven-property, 765,000-square-foot office portfolio that Shahbazi financed with $54.7 million in securitized debt from PNC Bank. Foreclosure auctions at the rest of the portfolio properties, located in Billerica and Chicopee, will be held in the next two weeks.

Additionally, another lender will auction a separate 271,000-square-foot portfolio of Shahbazi properties in Marlborough and Norwood next week.

Midland Loan Services seized a 525,000-square-foot portfolio in Wilmington and Lowell from Shahbazi’s firm, KS Partners, late last year.