A bus with a wedding party on board went off a mountain road in northern India and, according to media reports, fell at least 500 meters into a gorge.

At least 25 of the approximately 50 bus passengers died in the accident on Tuesday in the district of Pauri Garhwal in the state of Uttarakhand, the news channel NDTV and other media reported on Wednesday.

The ANI news agency quoted the state police chief Ashok Kumar as saying that police and civil protection could have rescued 21 people alive in a night-time rescue operation and taken them to hospitals. The cause of the accident was initially unclear.

The office of India's Prime Minister Narendra Modi called the accident "heartbreaking" and promised any help, Modi said in a tweet.