Hoax bomb threats targeting polling places and election offices briefly disrupted voting in five battleground states, with the FBI saying the threats in four of those states came from Russian email domains. The origin of the threats in the fifth state was not clear.

The threats targeted at least 50 sites across Georgia, Pennsylvania, Arizona, Wisconsin and Michigan, authorities said.

No bombs were found, and the few delays related to the threats appeared to have little impact on voting.

“The FBI is aware of bomb threats to polling locations in several states, many of which appear to originate from Russian email domains,” the FBI said in a statement Tuesday night. Email addresses associated with a foreign country’s domain are easy to make online by people located anywhere, and a country’s email domain’s being associated with a message does not mean it was sent from that country.

The Russian Embassy in the U.S. said any accusation that it was behind the threats was “vicious slander” and “nonsense,” according to the government-owned news service RIA Novosti.

German officials accused Russia of orchestrating bomb threats against several polling places in Moldova’s presidential elections last week. Experts say such threats could discourage voters from going to polling sites.

“The potential to have suppressed votes is a huge escalation,” said Bret Schafer, a senior fellow at the Alliance for Securing Democracy at the German Marshall Fund. ”Calling in a bomb threat takes things to a very different level than what we’ve seen them do in the past.”

If U.S. authorities conclude that Russia was behind the threats, “I don’t think anyone could look at this, regardless of party, and decide that this is not that big of a deal,” he said.

“It’s not totally clear yet, but there seems to be a playbook here,” added Schafer, who co-wrote an analysis earlier Tuesday saying Moscow might try the same approach it did in Moldova.

The emails and threats sent to the various states were similar in language and structure, according to a senior FBI official and a senior law enforcement official.

The largest number of threats appeared to target polling sites in Georgia. Fulton County received 32 bomb threats delivered in a variety of ways — some called 911, others dialed directly into target locations, and some were delivered via email, Fulton County Police Chief W. Wade Yates said.

A Fulton County Superior Court judge ordered five polling places to stay open less than an hour past their scheduled closing times to make up for evacuations.

Other threats were made to sites in DeKalb and Gwinnett counties, authorities said.

All told, about 10 polling places in Georgia were kept open 40 more minutes to make up for time lost to temporary evacuations, Secretary of State Brad Raffensperger said.

Delays related to the threats appeared to be short. A poll worker at the Etris Community Center in Union City told NBC News that the Fulton County center was evacuated suddenly around 9 a.m. for at least 45 minutes while local authorities cleared the building for safe re-entry.

The worker, who asked not to be identified because he was not authorized to speak publicly, said the majority of those evacuated “came back in and voted” after having waited in the parking lot. “That was a good thing,” the worker added.

Beyond Georgia, limited information about the threats was available Tuesday evening.

Arizona Secretary of State Adrian Fontes said in a briefing Tuesday evening that four bomb threats were emailed to polling sites in Navajo Country. They came from an email address with a Russian domain, Fontes said, but he cautioned that it did not necessarily mean the threats came from Russia. The threats were deemed not credible, he said.

“The motive appears to be to ensue chaos — not to impact any political outcome,” he said. “We don’t see anything in the pattern or the distribution that would make us think that this is to affect a political outcome.”

Police in Madison, Wisconsin, said they responded to emailed threats to several locations in the city, including current and former polling sites.

Threats to polling sites and election offices were reported across about a dozen Pennsylvania counties, where targeted polling sites were ordered to stay open late, officials said.

Philadelphia police said they received 911 threats at about 10 locations Tuesday evening. One polling site was briefly evacuated, so a judge extended voting times there for 23 minutes, police said.

Officials said state election offices and law enforcement agencies had anticipated bomb threats to polling places or other election-related sites and had prepared for them.

“Election officials and law enforcement have been planning for possible scenarios like this for the last couple of years, and their training has really shown,” said Lawrence Norden, vice president of the elections and government program at the Brennan Center for Justice at New York University Law School.

“But I think the number of these bomb threats is, if not surprising, very concerning,” he added. “The threats need to be investigated, and whoever is responsible must be held accountable.”