UPDATE: The super PAC tells the Reporter it's backing Annissa Essaibi George. Original story is available below.

A new super PAC, with a Boston focus, appears to be gearing up for an entrance into city politics as a mayoral preliminary election draws close.

The group on Wednesday filed paperwork with the independent Office of Campaign and Political Finance (OCPF), calling itself "Bostonians for Real Progress.” It was not immediately clear which political candidate, if any, the group may support.

The group listed the address of a Foxborough accounting firm that has been used by Danielle Allen, a Democrat running for governor, and a political action committee tied to former Congressman Joe Kennedy III.

The accounting firm is the same as that used by "Boston Turnout Project," a super PAC formed in May. That group, which has lain publicly dormant, listed as its chair a former aide to Sen. Elizabeth Warren. City Councillor At-Large Michelle Wu, one of the five major candidates running for mayor, is a longtime supporter of Warren.

The accounting firm did not respond to messages seeking comment. Carol R. Martinez is listed as the chair of the "Bostonians for Real Progress" super PAC.

In the “Purpose” section of the regulatory filing, the "Bostonians for Real Progress" group said, “To support candidates that want to build a more prosperous and equitable Boston for all citizens”

Its “specific interests” include “Economic Growth, Better Jobs, Affordable Rents, Reliable Transportation, The Best Public Schools and Safe Neighborhoods.”

Super PACs are flocking the Boston mayor’s race as five major candidates slug it out for two post-preliminary slots. The two winners of the Sept. 14 preliminary will face off in the Nov. 2 general election.

Since March, two super PACs have already formed and are actively supporting Acting Mayor Kim Janey and District 4 Councillor Andrea Campbell. The hospitality workers union, UNITE HERE Local 26, has created a super PAC for Janey, while donors, including Netflix founder Reed Hastings, are backing the “Better Boston” super PAC for Campbell.

The pro-Campbell super PAC recently posted to YouTube a second ad, “The System,” which touts her biography, as did its first ad, “Personal.”

Super PACs also played an outsized role in the 2013 race to succeed Mayor Thomas Menino, with the outside groups pouring millions into television ads and mailers supporting the two eventual finalists, state Rep. Marty Walsh and City Councillor At-Large John Connolly.

In that race, the source of the money was hidden from view until after the election. Campaign finance regulators now require super PACs operating in Massachusetts to regularly file reports on their donors and spending, as well as note the names of top donors in the ads.

This post was updated on Thursday, July 22, with additional information on the accounting firm.