Updated

Undercover government investigators were able to obtain thousands of dollars in taxpayer subsidies under ObamaCare using fake identities, according to findings presented to Congress on Wednesday.

The probe by the Government Accountability Office has raised fresh concerns about the ability of the sprawling health care program to prevent or intercept costly fraud schemes. In the case of the GAO investigation, 11 out of 12 applications submitted using "fictitious identities" were accepted, resulting in subsidized health coverage.

"For each of our 11 approved applications, we paid the required premiums to put policies into force, and are continuing to pay the premiums. For the 11 applications that were approved for coverage, we obtained the advance premium tax credit in all cases," the report said.

According to the GAO, the total amount for these credits was $2,500 monthly, adding up to $30,000 a year.

GAO officials testified about the findings before a House Ways and Means subcommittee Wednesday.

"We are seeing a trend with ObamaCare information systems: under every rock, there is incompetence, waste, and the potential for fraud," Rep. Dave Camp, R-Mich., chairman of the committee, said in a statement. "This law is already hitting Americans where it hurts the most - their pocketbooks. Now, this administration is forcing the American taxpayer to foot the bill for ObamaCare's waste and fraud."

Sen. Orrin Hatch, R-Utah, added: "Ironically, the GAO has found ObamaCare is working really well -- for those who don't exist."

The inquiries were carried out in several different states.

The administration pointed out that six of the GAO's fake online applications were blocked by eligibility checks built into computer systems at HealthCare.gov. Still, the GAO says its undercover agents found a way around that by phoning the call centers and were able to enroll anyway.

In six other applications, GAO investigators also tried to sign up fake applicants with in-person representatives. But in five of those cases, GAO was "unable to obtain in-person assistance" for various reasons, including one representative saying they could not help because HealthCare.gov was down.

"We are examining this report carefully and will work with GAO to identify additional strategies to strengthen our verification processes," administration spokesman Aaron Albright said. At least on paper, fraudsters risk prosecution and heavy fines.

The GAO said its investigators concocted fake identities using invalid Social Security numbers and falsely claiming citizenship or legal residence. In other cases, they made up income figures that would disqualify them from getting subsidies.

Among the findings:

--Contractors processing applications for the government told the GAO their role was not to ferret out potential fraud.

--Five of six bogus phone applications went through successfully. The one exception involved an applicant who refused to provide a Social Security number.

--Six online applications were snagged by an identity checking system. But investigators just dialed a call center and all six were approved. That seemed to be an open pathway to coverage.

The Associated Press contributed to this report.