Raigad, April 15 : At least 12 passengers were killed and 28 others injured when a private bus plunged into a gorge on the Mumbai-Pune highway on Saturday, officials said here. The accident occurred at around 4 a.m. on the Pune-Mumbai arm of the highway and the bus reportedly fell into the ravine at least 50 meters below, near the treacherous Borghat stretch. At that early hour, there was limited traffic on the highway but some people managed to rush to the accident spot, summoned the Raigad Police, Fire Brigade and local trekkers groups for help. A massive rescue operation was immediately launched with ropes and climbers going down to help the victims below, numbering around 40-45 including the bus driver, said the locals. According to the district authorities, the injured persons were rushed to the Khopoli Civil Hospital and the Jakotia Hospital, and the private MGM Hospital in Navi Mumbai for treatment. A Raigad Police official said that a majority of the passengers were members of the Baji Prabhu Music Group, Goregaon, and were returning home after performing at a programme in Pune on Friday. /IANS