State election officials across the U.S. are warning voters of a wave of unidentified robocalls and texts that suggest voters stay home.

Why it matters: The robocall campaign has sparked fresh fears that misinformation could spread on Election Day, targeting Americans' cellphones to scare them away from the polls.

The state of play: An estimated 10 million spam calls have barraged voters — especially those in battleground states — in recent days, according to the Washington Post.

• Voters reported receiving calls with a short, recorded message telling them to “stay safe and stay home.” The robocall campaign began this summer, according to the Post, sometimes with an estimated half-million calls going out each day and targeting some voters more than once.
• "The origins of ... the calls and texts remain unclear, reflecting the sophisticated tactics that robocallers typically deploy in order to reach Americans en masse across a wide array of devices and services," the Post writes.
• Data from tech company YouMail, which offers a robocall-blocking smartphone app, show that voters in 280 of the U.S.’s 317 area codes have received the calls.

What they’re saying:

• Federal Communications Commissioner Geoffrey Starkssaid Tuesday afternoon: "I'm going to get to the bottom of this. Illegal robocalls and robotexts that seek to impact our elections are unacceptable."
• Joe Biden's campaign spokesperson Bill Russo said of the calls: “We are aware of this issue and are using every tool at our disposal to remind voters that today is their last chance to make their voice heard in this election."

Meanwhile, state officials are scrambling to reassure voters in response to the flood of calls and texts.

• New York Attorney General Letitia James announced in a statement that her office is investigating allegations that voters are receiving robocalls that are suggesting people stay home.
• "Voters should rest assured that voting is safe and secure, and they should exercise their fundamental right to vote in confidence," James said. "We, along with state leaders across the nation, are working hard to protecting your right to vote, and anyone who tries to hinder that right will be held accountable to the fullest extent of the law.”
• Michigan Attorney General Dana Nessel said that some residents in Flint received calls falsely directing them to “vote tomorrow” citing long lines at the polls.
• “Dearborn voters, text messages are reportedly being sent to trick you into thinking there are ballot sensor issues,” Nessel tweeted. “Do not fall for it, it’s a trick!”
• Michigan Gov. Gretchen Whitmer said in a tweet: “Lines across the state are minimal and moving quickly … and leaders across state and local government will work quickly to stamp out misinformation trying to prevent Michiganders from voting."
• Florida Rep. Val Demings wrote: "False robocalls are spreading misinformation to try to silence your voice.Don’t be fooled:You must vote TODAY, before 7:00p (but stay in line if you’re in line at 7:00!)"
• Oregon Gov. Kate Brown also weighed in, tweeting, “Don’t believe the lies! Have your voice heard!”
• Nebraska Secretary of State Robert Evnen tried to reassure voters they would be "kept safe."

What's next: The FBI is reportedly investigating the robocall campaign, per the Post and Reuters.

• "We are aware of reports of robocalls and have no further comment," the FBI said in a statement to Axios. The agency encouraged voters to verify any election and voting information through local officials.