A probe by the Justice Department has determined that Iran was responsible for a 2013 cyberattack on a dam in the suburbs outside of New York City, and an indictment is expected soon, a U.S. official told The Associated Press Thursday.

The official, who was briefed on the investigation, spoke to the AP on condition of anonymity because the official was not authorized to speak publicly about the ongoing criminal investigation.

In 2013, hackers accessed the control system at the Bowman Avenue Dam, a small structure in Rye Brook, about 20 miles north of New York City, that's used for flood control.

The intrusion allowed the hackers to probe the system, prompting a federal investigation.

The official told the AP that investigators have determined Iran was responsible for the cyberattack and that an indictment is expected to be handed down in the case from the U.S. attorney's office in Manhattan. It wasn't clear whether the indictment would charge specific people within the Iranian government or publicly name Iran as being behind the attack. A formal announcement was expected to be made as soon as mid-April, the official said.

Officials in Rye said in December that they had been alerted by the U.S. Department of Homeland Security about unauthorized access to the city's computer system.

At a news briefing Thursday, State Department spokesman Mark Toner declined to specifically comment on the prospects that Iran would be charged in the cyberattack, but said: "I would say broadly that we obviously take all, seriously all such malicious activity in cyberspace. We're going to continue to use all the tools at our disposal to deter, detect, counter, and mitigate that kind of activity."

A spokesman for the Islamic Republic of Iran's Permeant Mission to the United Nations did not immediately respond to a request for comment Thursday night.