BOSTON – Developers who are unsuccessful in their pursuit of casinos in the eastern or western regions of Massachusetts could compete in the newly opened southeastern region under a plan approved by the state’s gaming commission Thursday.

The decision follows the panel’s recent vote to open up southeastern Massachusetts — known as Region C in the state’s 2011 casino law — to commercial casino bidders. The Mashpee Wampanaog tribe had previously enjoyed exclusivity in Region C while it pursued state and federal approvals for a tribal casino in Taunton.

The commission unanimously approved a request that could potentially give a second bite at the apple to companies that submitted initial applications but failed to negotiate host community agreements, or secured agreements that were later rejected by voters.

Under the plan, a developer could offer a new proposal in the southeast region without having to submit a new application or pay a second $400,000 entry fee — provided the company and its investors had cleared earlier background checks conducted by the panel. In some cases, a company could be required to amend its initial application to include any new partners or financial backers who were not part of its original proposal.

The casino law authorizes up to three resort casino licenses, one each in Region A (eastern Massachusetts), Region B (western Massachusetts) and Region C. It also allows for one slots parlor in the state.

It’s unclear if any of the current casino bidders might take advantage of the provision approved Thursday, since most are still negotiating agreements or awaiting referendums in their host communities. One company, Penn National Gaming, was shut out of pursuing a casino in Springfield after city officials opted to negotiate a host community agreement with MGM Resorts.

The commission Thursday reiterated its position that opening up southeastern Massachusetts does not preclude the Mashpee from pursuing its casino bid. “We are dedicated to not interfering with anything the tribe is doing as they move forward,” said Commissioner James McHugh.

The tribe is seeking a land-in-trust designation from federal officials for the Taunton site, and is awaiting a vote in the Legislature on a revised state casino compact it negotiated with Gov. Deval Patrick. Uncertainly surrounding the tribe’s bid prompted the commission to open the southeast region to commercial developers, but the panel has said it will consider the progress made by the tribe before it reaches the point of awarding a license.

The commission is considering a timetable that calls for initial applications for the southeastern license to be submitted in October, with an award possible by the end of 2014. Some commissioners said they would like to see that timetable accelerated so Region C does not fall too far behind other the two other regions, where casino licenses could be awarded by early next year.