CHENGDU -- Freak weather caused a boat to sink in Southwest China's Sichuan province earlier this year, an investigation report released Wednesday indicated.

The report from Sichuan Provincial Administration of Work Safety showed that sudden strong winds and heavy rain capsized the boat in Bailong Lake in Guangyuan city in June, killing 15 and injuring three others.

The report said that the boat owner Zhou Piqiang, who died in the accident, and lake managers failed to warn the passengers to wear life jackets. It also said that the local weather warning system was incomplete.

It suggested that 21 people be held accountable.