"New rescue teams are due to arrive and we are waiting for new data to help us tighten up the search area, which is very large," a police official told AFP.
Gautier was hiking near Policastro, some 200 kilometres south of Naples. He was last heard from on 9 August around 9:00 am, when he called emergency services on his mobile phone to say that he had fallen off a cliff and broken both his legs.
He was unable to give a precise location and lack of reliable data from his phone call meant that the search area extended over some 140 square kilometres, including across into Calabria.
"There are very few antennas in this uninhabited region that can allow a precise location of the past call," said the official.
There have been no signs of connection from his mobile phone since.
Social media has seen a flood of appeals for news of Gautier. A friend told investigators that he had left with reserves of food and water that could allow him to survive "more than 15 days ".
The 27-year-old student has been living in Rome for two years, writing a thesis in art history.
Nous savons désormais que #SimonGautier avait beaucoup de vivres et de l’eau sur lui permettant de survivre plus de 15 jours ! IL EST EN VIE. ON VA LE RETROUVER.Thomas Marsal (@marsal_thomas) August 17, 2019
PLEASE RT for ou #missing friend pic.twitter.com/ClN29w9UWv