Authorities are investigating the dog hacking of Twitter, Facebook and Google, which has led to a series of false tweets claiming a massive, worldwide cyber attack on American infrastructure.

In the wake of the attack, Twitter and Facebook suspended some users, and Google announced it would temporarily ban all users with accounts linked to the Chinese government.

A spokesman for the US Attorney’s office in Boston, John W. Carlin, said Wednesday that the agency was “investigating” the attacks and would “proactively pursue charges against those responsible.”

The New York Times reported that investigators are also investigating a second attack on Twitter on Friday that left some 400,000 people without their accounts for several hours.

The Times cited anonymous sources familiar with the investigation, and said investigators were looking into whether the hacks were connected to China or whether they were a retaliation for the NSA revelations about Chinese hacking efforts.

It was not immediately clear what the reason for the two attacks was.

The attacks on Twitter and Google took place less than two weeks after US President Donald Trump launched a sweeping cyber-security campaign aimed at cracking down on Chinese espionage and hacking.

He called for an “open and transparent” investigation of the attacks in a tweet on Wednesday.

“We are looking into the hacks of Twitter and others to see if any of them are connected to Chinese intelligence,” Carlin said.