Rescue forces received an emergency call about an accident on the ravine called Bukit Genting at 8:20 p.m. and arrived in the scene 10 minutes later, Strait Times reported.
They had difficulty in reaching the scene with fire engines, forcing them to climb onto the hill for 15 minutes with emergency equipment.
It took more than two hours to free the tourists out of the bus.
One Singaporean woman was confirmed dead at the scene while others were taken to nearby hospitals for treatment.
South West District Police Chief Supt Kamarul Rizal Jenal told Bernama the victims are believed to an elderly group who are on holiday in Penang.
The cause of accident was under investigation, he said.