Mayor Gray is mobbed by the media after a press conference on May 23. (Ricky Carioti/THE WASHINGTON POST)

Mayor Vincent C. Gray’s 2010 campaign inaccurately documented at least $100,000 in expenses in records filed with the D.C. Office of Campaign Finance, according to campaign treasurer Betty R. Brown.

In her first public comments since federal authorities launched an investigation into Gray’s campaign, Brown said a majority of the amount had been reported as one-time “polling/mailing list” payments to her but was actually doled out in cash payments to campaign field workers.

“The [ward] coordinators actually paid the money out to the workers,” Brown said.

Her comments underscore the extent of the legal troubles concerning Gray’s official mayoral effort, including guilty pleas from three associates in a federal probe of the campaign. Brown’s allegations show a cash-fueled effort to get out the vote for Gray (D) but one that can’t easily be deciphered in records filed with campaign finance officials.

According to the U.S. Attorney’s Office, more than $653,000 was secretly poured into a separate “shadow campaign” whose spending was never reported. The campaign finance office has expanded an audit of the campaign to review the unreported expenses detailed by prosecutors this week as well as the payments to campaign workers.

Brown would not say whether the records were intentionally mischaracterized or the result of shoddy bookkeeping by the campaign. It’s unclear how many workers were paid or whether their payments exceeded the $50 maximum set by city laws.

Several former campaign workers said longtime Gray associate Thomas W. Gore oversaw the assembling of the financial reports, including the filing of the documents with campaign finance staff members. He was the first Gray associate to plead guilty to federal charges as part of the ongoing investigation.

Brown acknowledged that she had been interviewed by investigators but said they did not talk about money distributed to field workers, including $50,000 on primary day. “They didn’t question me about that,” she said, adding that she is not concerned that she would be charged.

She declined to comment further about the investigation or her duties as treasurer. Gray did not return requests for comment.

This week, U.S. Attorney Ronald C. Machen Jr. said the 2010 mayoral race was “corrupted by a massive infusion of cash” that was concealed as part of the “shadow campaign.”

Several Gray campaign operatives have pleaded guilty to federal felonies related to illicit payoffs made to Sulaimon Brown, a mayoral candidate who alleges that he was paid to verbally harass then-Mayor Adrian M. Fenty (D). Gray had denied Brown’s allegations.

Gore faces 12 to 18 months in prison after admitting in May to shredding a notebook detailing secret payments to Sulaimon Brown. That same week, campaign aide Howard L. Brooks pleaded guilty to making a false statement and admitted his role in the payments to Brown.

Public relations consultant Jeanne Clarke Harris pleaded guilty this week to several charges, admitting that she helped orchestrate the “shadow campaign,” which was funded by $653,800 from local businessman Jeffrey E. Thompson. He has not been charged.

Harris confirmed to The Washington Post that she met with Gray in January but would not say what they discussed. People with knowledge of the meeting said they discussed unreported expenditures on behalf of his campaign. Gray later told her to submit them to his campaign staff, they said. It is unclear whether invoices were submitted or whether he knew of the source of the funding or the amount.

An article by the Associated Press on Thursday about official campaign payments to field workers corroborates Betty R. Brown’s assertion about how the cash was spent but mislabeled as other services.

Some of the campaign ward coordinators told The Post that they paid field workers $100 in cash each. Those payments would exceed the $50 limit. Also, The Post reported last year that the campaign violated the rules by collecting cash donations over the legal amount and that it had illegally turned some of the cash into money orders.

According to one worker, who spoke on the condition of anonymity to discuss matters freely, campaign volunteers and workers spent hours filling in blank money orders and forging the signatures of purported donors, including taxi drivers.

Gore and local businessman Dil Belay oversaw the writing sessions, the worker said.

Frederick D. Cooke Jr., Gore’s attorney, denied that his client oversaw or was present when workers allegedly completed the money orders. “It’s just not true,” he said, adding that he spoke to members of Gray’s finance team. Cooke would not identify the members with whom he spoke.

Belay did not respond to calls and e-mails. According to internal campaign files, he and Brooks were in charge of reaching out to taxi drivers for their support.

In some instances, workers questioned contributions recorded in their names and the names of others. Some of the names on an internal list of campaign contributors obtained by The Post do not appear on files recorded with the campaign finance office and vice versa.

One worker was listed as donating more than $1,000. When Gore was asked about it, he said it was considered “in-kind,” according to the campaign worker who requested anonymity to speak freely.

Cooke said he “never heard anything like that associated with [Gore].”