The Department of Homeland Security has declined to investigate Southern California Edison on allegations that it is replacing American employees with foreign workers on H-1B visas.

In response to a bipartisan call from ten U.S. senators led by Sens. Jeff Sessions (R-AL) and Dick Durbin (D-IL), U.S. Citizenship and Immigration Services — an agency within DHS —  said that while it is on the lookout for possible H-1B violations, an investigation into the company is “premature.”

“At this point, it would be premature for USCIS to speculate as to whether Southern Edison’s participation in the H-1B program has violated any laws,” USCIS Director Leon Rodriguez wrote in a letter dated Tuesday.

In a joint statement Wednesday Sessions and Durbin expressed disappointment in the reply to their request for an investigation and took issue with Rodriguez’s letter.

“The reply letter was non-responsive, failing to address the questions presented. Director Rodriquez merely stated that ‘it would premature for USCIS to speculate as to whether Southern California Edison’s participation in the H-1B program violated any laws.’ We did not ask for speculation; we asked for an investigation, and an explanation of any legal obstacles to conducting such an investigation,” the pair said.

“Why will the Department of Homeland Security not conduct one?” they continued. “Does DHS have insufficient legal authority to conduct such an investigation? This letter does not tell us. There are legions of displaced Americans formerly employed by Southern California Edison and many other companies who deserve answers.”

Earlier this month the ten senators called on Justice Department, the Department of Homeland Security, and the Department of Labor to look into abuses of the H-1B visa program.

“Congress has a responsibility to ensure that the law does not permit employers to abuse our visa programs to undercut domestic wages and workers. If USCIS believes existing law does not prevent these activities, then the law must be changed,” Sessions and Durbin argued Wednesday.

Last week the Labor department also declined to investigate. The senators are still waiting for a response from the Justice Department.