Major British newspapers recently claimed the Red Bull driver has inked an agreement to switch to Ferrari in 2014.
Italian television Mediaset's Italia1 channel now agrees, citing the information of the well-connected and authoritative journalist Giorgio Terruzzi.
Fabio Seixas, the correspondent for Brazil's Folha de S.Paulo newspaper, thinks the news could be good for Felipe Massa, given that Vettel will not be arriving until 2014.
"For me, Sergio Perez would not accept going (to Ferrari) only for 2013. For Ferrari, it is more convenient to keep Massa for another year.
"This time of year is known as 'silly season', where most of the rumours are not true," Seixas explained. "But experience says that when a rumour comes from so many different sources, it does often materialise."
But the correspondent for another Brazilian newspaper, O Estado de S.Paulo newspaper, said that in his view, the Vettel-to-Ferrari rumour is obviously untrue.
Nonetheless, Livio Oricchio described Mediaset's Terruzzi as a "friend" he has known for "two decades".
"I find it strange that Giorgio states categorically that Vettel is already signed with Ferrari. He is always very cautious with these issues," he said.
"My argument is that the story makes no sense for anyone."