The front end of a car was visible next to it, its two tyres suspended in the air over the edge of the cliff.
The landslide covered the road below leading into town.
Conti said local authorities were working with police, fire and civil protection units to assess the next steps, including the resumption of school, which was cancelled.
“The situation is dire,” said the mayor.
Italy’s civil protection unit said all residents in a 4km radius of the landslide had been evacuated.
Niscemi, which has a population of more than 27,000 people, is located about 28km inland from the southern coastal city of Gela.
Coastal areas of Sicily were hit last week by Storm Harry, damaging seaside roads and residences.
Today the region’s president, Renato Schifani, estimated the cost of the damage, including that from the Niscemi landslide, at more than €1.5 billion.
Italy has declared a state of emergency for the southern regions of Sicily, Sardinia and Calabria .
During a Cabinet meeting, the Government decided to allocate €100 million for the “first urgent interventions”, Prime Minister Giorgia Meloni said on social media.
-Agence France-Presse