According to a news report from Reuters, Yahoo last year designed custom software that searched all of its customers’ incoming emails for specific information provided by U.S. intelligence officials.

Yahoo is currently in the process of being taken over by Verizon Communications in a $4.8bn (£3.8bn) deal. “Yahoo is a law abiding company, and complies with the laws of the United States,” the company told Reuters, while Verizon declined to comment.

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The allegation is just the latest twist in the former internet titan’s story. Yahoo was forced to admit less than two weeks ago that millions of its customers’ information was stolen by hackers back in 2014.

The company complied with the classified U.S. government order, scanning hundreds of millions of Yahoo emails. US law allows domestic intelligence agencies such as the NSA and FBI to order the release of customer data that they believe could prevent a terrorist attack.

Other U.S. phone and Internet companies have previously admitted to handing over bulk customer data to intelligence agencies. But experts have commented that they had not seen any need before for the creation of a new program to be specifically written for such a request.

According to some sources, the decision to comply with the US government order, resulted in the 2015 departure of chief security officer, Alex Stamos leaving Yahoo, as he disagreed with the rest of the board’s decision not to appeal against the edict. Stamos now works for Facebook.

Both Google and Microsoft separately stated they had not conducted such email searches when asked, but then even if they had, current US law would prohibit them from admitting it. Experts have also said it is unlikely however, that Yahoo is the only internet company that the NSA and FBI approached with the same demands.