“Our security team has investigated this incident and we have no evidence of an unauthorized intrusion or compromise of Ring’s systems or network,” the statement said. “Recently, we were made aware of an incident where malicious actors obtained some Ring users’ account credentials (e.g., user name and password) from a separate, external, non-Ring service and reused them to log in to some Ring accounts.”

Ring users can monitor the cameras on the company’s smartphone app and speak to people inside their home and at their front door using a two-way audio feature. But cybersecurity experts say all it takes is a user name and password for hackers to gain access to the devices.

Ring said it began sending emails this weekend to its millions of customers, reminding them to use multifactor authentication, which requires users to verify their identity by entering a code that they receive as a text message or by using an authentication application, in addition to their password.

“Unfortunately, when the same user name and password is reused on multiple services, it’s possible for bad actors to gain access to many accounts,” the statement said.

A spokesman for the Jackson, Miss., field office of the F.B.I. said he could not confirm or deny that the episode was being investigated. The Southaven police chief, Macon Moore, said on Monday that the case was under investigation, but would not comment further because the investigation was active. He also said that the police had not received other reports.

Cybersecurity experts said it’s not that difficult for hackers to gain access to “internet of things” devices, which include Ring security cameras and voice assistants, such as Alexa and Google Home.

“Unfortunately, we’re so reliant on passwords at this point, but passwords are absolutely the weakest link,” said Tim Weber, security services director for ADNET Technologies in Farmington, Conn.