Le Monde also reported that the January 7 Charlie Hebdo massacre nearly was canceled the day before, because one of the attackers was sick.
The newspaper cited unnamed French investigative sources for both accounts. Le Monde reported that it didn't know the message's content, but said it helps to show the Charlie Hebdo attacks by Cherif and Said Kouachi
and supermarket attack by Amedy Coulibaly were coordinated -- something that Coulibaly himself purportedly admitted to a TV reporter before police killed him.
Cherif Kouachi sent a text message to Coulibaly at 10:19 a.m. on January 7, Le Monde reported. That is a little more than an hour before the Kouachi brothers assaulted the magazine offices in Paris, killing 12 people and injuring 11.
Coulibaly, who authorities say was a known associate of the Kouachi brothers, shot a policewoman to death in a Paris suburb on January 8, and then took hostages -- killing four -- at a kosher supermarket in Paris on January 9 before police shot and killed him in a raid on the store.
The Kouachi brothers were killed the same day, as police moved in to end a separate siege north of Paris.
The January 7 text message was sent from Cherif Kouachi's phone on the outskirts of Paris to one of 13 phones that Coulibaly was using, according to Le Monde, citing its investigative sources.
Le Monde said investigators determined that Coulibaly's phone was bought specifically to communicate with the Kouachi brothers, and that only six messages had been sent from the device.
Evidence from the phone shows that Coulibaly and Cherif Kouachi probably met in person sometime before 1 a.m. on January 7, Le Monde reported.
The investigative sources told Le Monde that the Charlie Hebdo attack almost was called off on January 6, because Said Kouachi had come down with the stomach flu.
Al Qaeda's Yemen affiliate, al Qaeda in the Arabian Peninsula, has claimed to be behind the Charlie Hebdo massacre.
Coulibaly, meanwhile, proclaimed his allegiance to the Islamic State in Iraq and Syria, or ISIS
Coulibaly, during the supermarket attack, told a journalist with CNN affiliate BFMTV by phone that he had synchronized his attacks with the Kouachi brothers
, BFMTV reported.