Authorities are reportedly investigating whether a retired federal agent knew about a white supremacist’s plans to carry out his deadly attack at a Buffalo supermarket 30 minutes before the crazed gunman went on the rampage.

Two law enforcement officials with knowledge of the probe told the Buffalo News that the feds believe the former agent — believed to be from Texas — was among at least six people who regularly communicated with alleged gunman Payton Gendron online about his racist views.

The sources said Gendron had also invited some online acquaintances to read about his hate-fueled, imminent plan to attack the Tops Friendly Markets store, where he allegedly killed 10 people and left three others injured on May 14.

Eleven of those shot were black and two were white. One dead victim was a retired Buffalo cop.

The Buffalo News said it could not determine if the retired agent accepted the invitation.

“These were like-minded people who used this chat group to talk about their shared interests in racial hatred, replacement theory and hatred of anyone who is Jewish, a person of color or not of European ancestry,” one of the officials told the news outlet.

“What is especially upsetting is that these six people received advance notice of the Buffalo shooting, about 30 minutes before it happened,” the source said.

“The FBI has verified that none of these people called law enforcement to warn them about the shooting. The FBI database shows no advance tips from anyone that this shooting was about to happen,” the official added.

The FBI is trying to track down the six people, who may be charged as accomplices in the shooting, the sources told the newspaper.

John Elmore, a civil rights attorney representing the family of Andre Mackniel, 53, one of the dead victims, told Fox News that if the retired agent “had advance notice, he had a moral obligation to get on the phone and try to notify someone about it.”

It was previously reported that 15 people accepted Gendron’s invitation to a private chatroom — chillingly named “Happening: This is not a drill” — where he allegedly spent months meticulously planning his attack.

He invited people on the Discord app 30 minutes before the massacre, CNN has reported.

The chatroom included months of posts written by an author who identified himself as Gendron, describing his twisted views and outlining how he’d scouted the Tops Friendly Markets in a crazed plan to kill as many black people as possible.

The Washington Post reported that 15 people had accepted the invitation, citing a person with knowledge of the messaging platform’s probe.

A copy of the invite reviewed by the paper said the accepted users also could view a video stream of the shooting through a link to an account on Twitch, a video streaming service where Gendron allegedly broadcast video of his attack.

A Discord rep told CNN: “What we know at this time is that a private, invite-only server was created by the suspect to serve as a personal diary chat log.

“Approximately 30 minutes prior to the attack, however, a small group of people were invited to and joined the server. Before that, our records indicate no other people saw the diary chat log in this private server,” the spokesperson added.

Gendron has pleaded not guilty to one count of murder in the deadly shooting, which he livestreamed on Twitch while wearing military-style tactical gear.

New York Attorney General Letitia James has said her office would investigate Discord, Twitch, 4chan and other platforms that the shooter “used to amplify” the rampage.