Thirty-six people were injured, 10 of them seriously, in what police called Israel's deadliest road accident.
The bus was taking 56 members of a singles club from central Israel on an outing when the first heavy rain in months began falling, leaving the road slick. The bus was traveling between the towns of Tiberias and Nazareth when the driver lost control.
Tour guide Zvika Mena told Israel TV that he was talking to the group when the bus veered off the road.
"Suddenly the bus began to zig-zag," Mena said. "I shouted to everybody to hold firm. There were loud shouts and panic. I was thrown out of the front window."
The red-and-white bus plunged at least 60 feet into the ravine and overturned, landing on its roof. Several bodies were pinned under the vehicle and some surviving passengers were trapped in their seats. Belongings were strewn across the rocky slope.
Hampered by heavy rain, rescue workers used metal cutters to free trapped passengers.
The bus was traveling just below the 50 mph speed limit, but that was too fast considering the road conditions, traffic police chief Yaakov Ganot said. Survivors said they had asked the driver several times to slow down.
The 26-year-old driver had worked for the bus company for six months and had been given several traffic tickets for minor offenses, Israel TV reported.