WASHINGTON (Reuters) – The Obama administration is expected to blame Iranian hackers as soon as Thursday for a coordinated campaign of cyber attacks in 2012 and 2013 on a suburban New York City dam and several other targets, sources familiar with the matter have told Reuters.

In one of the largest foreign cyber attack cases since 2014 when the United States charged five Chinese military hackers, the U.S. Justice Department has prepared an indictment against about a half-dozen Iranians, said four sources, who spoke on condition of anonymity due to the sensitivity of the matter.

The charges, related to unlawful access to computers and other alleged crimes, were expected to be announced publicly by U.S. officials as soon as Thursday morning at a news conference in Washington, the sources said.

The indictment was expected to directly link the hacking campaign to the Iranian government, one source said.

Though the breach of back-office computer systems at the Bowman Avenue Dam in Rye Brook, New York has been reported, it was only part of a hacking campaign that was broader than previously known, as the indictment will show, the sources said.

In the intrusion of the dam computers, the hackers did not gain operational control of the floodgates, and investigators believe they were attempting to test their capabilities.

The dam breach coincided roughly with attacks on U.S. financial institutions. Cyber security experts have said these, too, were perpetrated by Iranian hackers against Capital One, PNC Financial Services and SunTrust Bank. Prosecutors were considering including those breaches in the indictment, sources said.

The hackers who were expected to be named in the indictment all reside in Iran, one source said.

The Justice Department declined to comment.

The indictment would be the Obama administration’s latest step to confront foreign cyber attacks on the United States. President Barack Obama accused and publicly condemned North Korea over a 2014 hack on Sony Pictures and vowed to “respond proportionally.” No details were made public of any retaliation.

James Lewis, a cyber security expert with the Center for Strategic and International Studies think tank, said, “We need to make clear that there will be consequences for cyber-attacks and that the Wild West days are coming to an end.”

Two weeks ago, it was widely reported that U.S. prosecutors were preparing an indictment against Iranian hackers related solely to the dam attack.

The broader indictment would come at a time of reduced tensions between the United States and Iran after a landmark 2015 nuclear deal. At the same time, the Obama administration has shown a willingness to confront Tehran for bad behavior.

Charging the Iranian hackers would be the highest-profile move of its type by the Obama administration since the Justice Department in 2014 accused five members of China’s People’s Liberation Army with hacking several Pennsylvania-based companies in an alleged effort to steal trade secrets.

(Reporting by Dustin Volz in Washington and Nate Raymond in New York; additional reporting by Mark Hosenball in Washington and Jim Finkle in Boston; Editing by Kevin Drawbaugh and Jonathan Oatis)