What the move means for the company was unclear. Its representatives also could not be reached for comment.
Adderly said he visited the property, on the Avenue of the Arts, earlier Tuesday and said the theater still appeared to be open to the public.
The company produces contemporary plays and musicals. On the schedule this month is the Philadelphia opening of a one-man show by the comedian Colin Quinn that was praised by critics during its run in New York City. That show runs from June 13 through July 6. The theater also offers performances by other Philadelphia artistic groups, such as the Koresh Dance Company.
The theater is named for Suzanne Roberts, wife of Comcast Corp. founder Ralph Roberts. The couple provided a $4.5 million gift to the company in 2006 and have been trying to find a way to continue to help it.
The company, which moved into the 365-seat venue in 2007, was supposed to pay for the building with a fund-raising campaign, but the economy cratered and donations dried up.
By 2012, the company owed more than $11 million to TD Bank and stopped making payments.
The Robertses pledged $1 million over five years, and in 2012, they offered $5 million to be held as an endowment by a third party, with the company annually receiving either $250,000 or 5 percent of the endowment, whichever was greater.
Recently, they hired outgoing Kennedy Center president Michael M. Kaiser to examine the company's finances and operations, and determine if it can be viable.
Kevin Feeley, spokesman for the couple, said the report "is almost complete" and should be done in the next week or two.
"At that point, the Roberts plan is to use the study as a basis for their future support of the theater," Feeley said.
NAI Mertz created an advertisement that shows the front of the theater and states that a "prime location on the Avenue of the Arts" is for sale.
The ad describes the property as having 32,505 square feet, including second- and third-floor offices and storage rooms.
The property also has 3,000 square feet of unfinished area that was "planned for an additional intimate venue."
It is part of the Symphony House condominium development, but is considered a separate unit, Adderly said.