Convicted former D.C. Council member Harry Thomas Jr. may have had help from someone in city government when he stole nearly $350,000 from a nonprofit, a council report has concluded.

But in the extensive report, to be released Friday, the council’s Committee on Human Services said it did not have enough information to name anyone who could have provided that assistance. The report faults officials at the Children and Youth Investment Trust Corp. for failing to detect the fraud.

Thomas, a onetime rising star in District politics, pleaded guilty in January to using trust funds intended for youth sports for personal use, including trips and a sport-utility vehicle. He faces 37 to 46 months in prison under federal guidelines when he is sentenced Thursday.

The preliminary report raises as many questions as it answers, prompting committee Chairman Jim Graham (D-Ward 1) to request that the council grant him subpoena authority so he can compel more witnesses to testify. “It is only by that authority that we will be able to obtain information necessary to the objectives of this investigation,” the report states.

The committee examined how Thomas was able to divert money through the trust. Its conclusions come amid federal investigations into donations to Mayor Vincent C. Gray’s 2010 campaign and contributions to several council members.

“Former Council member Thomas is being held accountable for his actions,” the report states. “However, we find that his criminal actions could not have occurred without the actions of Trust staff and perhaps others.”

The report, a copy of which was obtained by The Washington Post, portrays the trust as an organization that gave Thomas preferential treatment and did not abide by its own rules, inappropriately accelerated payments to a group Thomas controlled, had lax oversight over how taxpayer money was used, and succumbed to influence from a top Thomas staffer, Neil Rodgers.

The council’s analysis also questions whether Gray, then council chairman, and council member Tommy Wells (D-Ward 6), who then headed the Human Services Committee, should have more closely scrutinized Thomas’s interaction with the trust.

The nonprofit was created in 2000 by Mayor Anthony A. Williams as a quasi-public agency that would more efficiently get public and private dollars to support disadvantaged youth.

Thomas’s scheme began after he convinced his colleagues to approve $400,000 in 2007 for “youth baseball programs” as part of $12 million in earmarks council members awarded to favored projects. But the report, based on more than 1,500 e-mails and numerous interviews, concluded that Thomas’s earmark was the only one approved by the council “with no specific grantee.”

“Those responsible for close supervision of [the budget] were surely aware of this anomaly,” the report states.

Wells, according to the report, recalls meetings with Gray “directly relevant to these issues” in 2007 and 2008. But Wells, the report states, now “has an uncertain recollection of what was said.”