U.S. to blame Iran for cyber attack on small NY dam: CNN

Citing unnamed U.S. officials familiar with the investigation, the network said the Justice Department had prepared an indictment and an announcement could come in the next week.

U.S. officials say the hackers gained access only to some back office systems, not the operational system of the Bowman Avenue Dam, a flood control system around 30 miles (50 km) north of New York City, and the attack was not considered sophisticated, CNN said.

A Justice Department spokesman said he had no comment about the report.

Asked about the report at a news briefing, State Department spokesman Mark Toner said: "We obviously take seriously all such malicious activity in cyberspace. We are going to continue to use all the tools at our disposal to prevent, deter, detect, counter, and mitigate that kind of activity."

CNN said the attack alarmed Obama administration officials, who said it occurred at a time that Iranian hackers were also conducting "similar probing attacks on U.S. financial institutions."

(Reporting by Mark Hosenball and Eric Beech; Editing by Alistair Bell)