Pressure continues to mount on Yahoo as repercussions from the recently announced massive breach stack up. Six democratic senators have written a scathing letter to Yahoo CEO Marissa Mayer, calling the delay in reporting the 2014 breach of over 500 million user accounts “unacceptable.”

The lawmakers include Senators Elizabeth Warren (MA), Edward J. Markey (MA), Al Franken (MN), Patrick Leahy (VT), Ron Wyden (OR) and Richard Blumenthal (CT).

The lawmakers said they were bothered by the length of time it took Yahoo to detect the intrusion, demanding to know if the US government had warned Yahoo of a possible state-sponsored hack.

“We are even more disturbed that user information was first compromised in 2014, yet the company only announced the breach last week,” the lawmakers said.

Yahoo said it detected the breach this summer after conducting a security review prompted by an unrelated hack claim that turned out to be false.

Other lawmakers have earlier called for a probe on Yahoo, including Senator Blumenthal who called for an investigation of the internet firm by the FBI, and Senator Mark Warner who asked the U.S. Securities and Exchange Commission to investigate whether Yahoo and its senior executives fulfilled obligations to inform investors and the public about the hack.