"The H-1B visa is one programme that really puts American workers at risk," Senator Chuck Grassley, chairman of the powerful Senate Judiciary Committee, said during a Congressional hearing on homeland security on Tuesday.
Noting that the population of H-1B workers in the US has been growing for decades, Mr Grassely said with that growth comes an increased possibility for fraud or abuse.
"...both of which I have seen and called on the Department of Homeland Security, with the help of Department of Justice, to investigate and prosecute," he said.
Mr Grassely even looked to put blame on the H-1B workers for "stagnation" of salaries in the technology sector.
"The vast majority of these H-1B workers are employed in the technology sector, and we've seen salaries in that industry stagnate for decades, at the same time the number of foreign tech workers keeps growing," he said.
The senator said he was encouraged that Citizenship and Immigration Services has announced several H-1B initiatives "designed to protect American workers".
"I hope that the United States Citizenship and Immigration Services (USCIS) would continue with its efforts to reign in abuses in a variety of foreign worker immigration categories," said Mr Grassley.
Ms Nielsen did not give a direct answer to this. However, she did say the Department was looking into all of the visa categories.
Mr Hatch also asked Ms Nielsen about news reports on cancelling three-year extensions for H-1B visa holders who are being sponsored for green cards - which can be a time-consuming process due to per-country green card limits.
"I believe that Congress previously addressed this issue in 2000, and indicated its intent to allow such extensions. Can you tell me if the department is, in fact, considering ways to stop granting these three-year extensions? And, if so, why? And I'd also be interested in hearing the department's explanation of how ending these extensions squares with the 2000 law," Mr Hatch asked.
"I'm not familiar with the very specific example on H-1B, but I will get back to you immediately after this," replied the Secretary of Homeland Secretary.
The curb on H-1B visa extensions could result in self-deportation of an estimated 500,000-750,000 Indian Americans. The proposal, which was part of President Donald Trump's "Buy American, Hire American" initiative that he vowed to launch on the campaign trail, is being drafted by Department of Homeland Security leaders, according to reports.