Researchers in Italy say they may have found traces of a Leonardo Da Vinci work hidden under a Florentine fresco.
Tiny probes, sent through drilled holes in Giorgio Vasari's The Battle of Marciano in the Palazzo Vecchio, found black pigment also used in the Mona Lisa, project workers claimed.
"These data are very encouraging," said the project's leader Maurizio Seracini.
But historians at a press conference in Florence stressed their research was "not conclusive".
They added that further chemical analysis needed to be carried out.
"Although we are still in the preliminary stages of the research and there is still a lot of work to be done to solve this mystery, the evidence does suggest that we are searching in the right place," said Seracini, who works at the University of California in San Diego.
The probes also discovered red lacquer and brown pigment on the hidden wall.
The research has been controversial, with some art experts signing a petition to stop the investigation because the drilling is damaging Vasari's existing work, BBC reported.
