Chinese President Xi Jinping has ordered all-out efforts to treat the injured and comfort the families of the dead after a factory blast on Saturday.

As of 9 p.m., the explosion, which happened at 7:37 am, has left 69 people dead and more than 180 others injured after ripping through a factory in east China's Jiangsu Province.

More than 200 workers were on the site when it happened.

Xi has demanded a full investigation into the accident and harsh punishments for those responsible.

Premier Li Keqiang has ordered safety checks to avoid similar tragedies from happening again.

Local officials said the explosion was a work safety accident, and the blast was probably caused by flames igniting dust inside the workshop.

Two senior executives at Kunshan Zhongrong Metal Products Co., Ltd have been placed under police custody.

President Xi and Premier Li have assigned state councilor Wang Yong to lead a State Council working team to Kunshan to look into the accident.

Upon arrival at Kunshan on Saturday afternoon, Wang visited the accident scene and was briefed by local officials about the latest developments.

Wang said relevant authorities and parties must learn from the bitter lessons to prevent similar accidents with resolute and vigorous measures.

He also urged careful check of the number of people at the spot and exhaustive search and rescue.

Moreover, prompt investigation should be launched and those liable for the blast must be seriously punished, Wang said, promising timely, accurate and transparent disclosure of information.

Local health authorities said most of the injured suffered burns and have been treated in hospitals in Kunshan and the nearby cities of Suzhou, Wuxi and Shanghai.