As Congress considers renewing a visa program for wealthy foreigners, government auditors say the program needs better oversight by the Department of Homeland Security to deter fraud and clarify how much it benefits the U.S. economy.

At issue is the EB-5 immigrant investor program, which allows foreigners to get green cards by investing at least $500,000 in American businesses, as long as the money creates at least 10 jobs. Congress created the program in 1990 as a way to stimulate the economy, but legislation authorizing it is set to expire Sept. 30.

In a recent report requested by members of Congress, the U.S. Government Accountability Office found that while DHS has taken steps to root out fraud and determine the program’s economic benefits, the agency could be doing better.

The report said that U.S. Citizenship and Immigration Services, which is part of DHS, “faces significant challenges” in detecting fraud, in part because it relies heavily on paper-based documentation and the electronic databases it does use contain limited information on applicants. EB-5 is susceptible to fraud, the report said, because it is difficult to identify the sources of funds immigrant investors use and whether they are from illicit sources such as the drug trade.

While the report did not provide fraud statistics, it said that the Securities and Exchange Commission received more than 100 tips about possible EB-5-related securities fraud violations from January 2013 through January 2015.

Citizenship and immigration services has reported that EB-5 created at least 73,730 jobs and pumped more than $11 billion into the U.S. economy from 1990 to 2014, the report said. But it cast doubt on those numbers, saying the agency’s methodology for calculating economic benefits was invalid and may, in some instances, “overstate some economic benefits derived from the EB-5 Program.”

Unions and immigrant advocates, who recently held a series of press conferences questioning whether EB-5 creates as many jobs as advertised, seized on the report’s findings. Union officials have also said the jobs the program does create don’t benefit the nation’s 11.3 million illegal immigrants, some of whom work on the projects.

“The stated rationale for the EB-5 program is job creation,” said Isaac Ontiveros, a research analyst for UNITE HERE, a union that represents nearly 300,000 hotel, casino and food service workers. “UNITE HERE is troubled by the GAO’s findings that USCIS does not use a valid and reliable methodology for reporting EB-5 program outcomes and economic benefits, including job creation.”

He called on Congress to “fix some of the problems with EB-5” as it debates reauthorizing the program in coming weeks. Congressional Republicans and Democrats recently proposed a series of reforms, including tightened oversight of companies that arrange the investments from foreigners.

EB-5 is supported by business groups, and has increasingly been used in recent years by real estate developers and other firms seeking foreign investors. In the District, for example, investors have put up more than $110 million and created more than 1,500 jobs through projects such as the Marriott Marquis Convention Center hotel, according to a trade group that backs the program.

The EB-5 Investment Coalition, which advocates for the program, said in a statement that “robust oversight and transparent processes are critical” to ensure that the program “can continue to serve its fundamental purpose of creating jobs for Americans.”

While the coalition praised citizenship and immigration services’s stewardship of the program, it said that coalition members — including the U.S. Chamber of Commerce and the National Association of Homebuilders — support “common-sense reforms that enhance national security, compliance and accountability within the program.”

In a joint statement, DHS and citizenship and immigration services said they “remain committed to preventing fraud and ensuring the integrity of the EB-5 Program.”

Citizenship and immigration services “has already taken steps to enhance fraud risk management, including the establishment of a specialized unit to provide additional oversight and conduct fraud, national security, and intelligence assessments,” the statement said. “We are pleased that GAO’s report recognizes these actions.”

The statement added that citizenship and immigration services concurs with recommendations made by GAO to strengthen fraud prevention “and to more accurately assess and report on program outcomes and the overall economic benefits of the program.”