Potential buyers of the Chicago Sun-Times have one more week to make a bid against Tronc Inc., the owner of the Chicago Tribune.

“With continued interest in the Sun-Times, we are working through the due diligence phase of the process with interested parties,” Sun-Times Publisher and Editor in Chief Jim Kirk said in an email to employees on Monday afternoon.

“That work will continue through this week,” Kirk said. “We have agreed with the Department of Justice that bids for the company would be due at the end of business on Monday, June 19.”

Last month, Tronc announced that it had agreed on a letter of intent to buy the Sun-Times, Chicago Reader and other media assets owned by Wrapports LLC.

The Justice Department’s Antitrust Division required the Sun-Times to publish an advertisement seeking more potential buyers to step forward by June 5. In a memo last week, Kirk said Wrapports “received communication from multiple parties” by the deadline.

One bidder has been identified as Edwin Eisendrath, a Chicago businessman and former 43rd Ward alderman, who filed a letter of intent to bid in partnership with the Chicago Federation of Labor, a source close to the bidding process told the Sun-Times.

It’s unclear whether the Eisendrath group is the only one to bid besides Tronc. Billionaire Neil Bluhm’s family was another potential bidder, according to a report by Crain’s Chicago Business. But media columnist Robert Feder reported that the Bluhms didn’t submit a bid.

Traditionally, the federal government has frowned upon a single entity controlling multiple media operations in the same market — concerns that both Tronc and Wrapports have tried to ease by saying the Tribune and Sun-Times would continue to operate as separate, independent voices should a deal go through.

The Chicago News Guild has been opposed to a Tronc-Wrapports deal. The union has launched a “#NoNewsMonopoly” Facebook page and Twitter hashtag campaign.

Details about the Chicago Federation of Labor’s involvement in Eisendrath’s bid were unclear. The CFL is an umbrella organization that represents 300 unions across Chicago and Cook County with a total membership of about 500,000 workers.