A minibus slid 20 meters down a mountain slope in eastern Japan on Friday, injuring 14 passengers, police said.

The bus, carrying 18 tourists aged over 50 who came to climb Mt. Eboshidake, started moving while the driver was outside the vehicle around 2:50 p.m. after he parked it in a lot at the trail entrance in the village of Nanmoku, Gunma Prefecture, according to the police.

The police initially said four people were seriously injured and 10 sustained light injuries but later corrected the numbers to three and 11, respectively. All the people are conscious, they said.

The police arrested the 66-year-old driver of the bus, Isao Ebihara, on suspicion of professional negligence. Ebihara told investigators he may not have fully engaged the parking brake, the police said.

The mountain is popular with tourists around this time of year, when pink azaleas are in full bloom.