U.S. authorities have launched an investigation into alleged violations of H-1B visa rules by Infosys and Tata Consultancy Services (TCS), two of India's largest technology companies. The Labor Department will look into reports that the two companies used the H-1B visa program to replace hundreds of American workers at electricity supply company Southern California Edison with immigrants holding the temporary work visas.

“A number of U.S. employers, including some large, well-known, publicly-traded corporations, have laid off thousands of American workers and replaced them with H-1B visa holders. … To add insult to injury, many of the replaced American employees report that they have been forced to train the foreign workers who are taking their jobs,” U.S. senators Jeff Sessions and Dick Durbin reportedly said on Thursday. “We’re pleased to hear that the Labor Department is taking a first step to stanch this tide of visa abuse.”

Under H-1B visa rules, U.S. companies can employ foreign workers in “specialty occupations” that require theoretical or technical expertise in specialized fields. While the program is intended to help businesses bring in high-skilled workers to fill positions for which American workers are not available, companies have, in the past, been accused of misusing it to bring in foreigners who would do the same work for less money.

In October, over 250 Disney employees were laid off and required to train their replacements -- immigrants on H1-B visas -- to do the jobs they had lost, the New York Times reported.

In this particular case, Southern California Edison is believed to have laid off more than 500 workers, replacing them with immigrants brought in by the Indian firms.

“Though such reports of H-1B-driven layoffs have been circulating for years, their frequency seems to have increased dramatically in the past year alone,” the U.S. senators reportedly wrote in an earlier letter to the Department of Justice, the Department of Homeland Security and the Department of Labor.

According to recent government figures, applications for H-1B visas reached a record 233,000 in the fiscal year 2016. Currently, a maximum of 85,000 of these work visas are available each year under limits set by Congress.