NEW DELHI -- At least 21 people, most of them school children, died after a houseboat carrying over 35 passengers capsized in India's southern state of Kerala late Sunday evening, local police confirmed early on Monday.

The accident occurred off the coastal town of Tanur in Kerala's Malappuram district. Around ten people have been rescued so far, and the rescue operation is still ongoing, a senior police officer told Xinhua over the phone.

Most of the deceased were children who had come for a ride amid ongoing school vacations, the Press Trust of India quoted Kerala Sports Minister V. Abdurahiman as saying.

The exact cause of the accident is not known yet.

Both Prime Minister Narendra Modi and President of India Droupadi Murmu expressed grief at the accident and sent condolences to the bereaved families.

An ex-gratia of 200,000 Indian rupees (around 2,447 US dollars) from the Prime Minister's National Relief Fund would be provided to the next of kin of each deceased, tweeted the prime minister.