Yuhang district police in Hangzhou, Zhejiang province, have summoned for questioning the people involved in the death of a woman who came into contact with hydrofluoric acid, local authorities said on Thursday.

According to a statement released by the Yuhang district branch of the Hangzhou Public Security Bureau, the female victim, surnamed Tu, was accompanying two female friends to plant vegetables in a derelict area on Sept 9. Tu stepped on and broke a white square plastic barrel while walking along a hillside where a house used to stand, bringing her foot into contact with the hydrofluoric acid inside, resulting in severe burning pain. Her friends fetched water to rinse the affected area and then brought Tu to her husband, who brought her to the hospital.

A statement from Hangzhou's Xianlin subdistrict said the 52-year-old Tu died on Sunday from side effects of contact with the chemical.

An investigation uncovered two additional plastic barrels of the same type and fragments of a cardboard box packaging. The site was previously a single-story house where a man surnamed Ai from Hubei province had resided from 2013 to 2015. The three barrels of hydrofluoric acid were placed there by his son, who worked in exterior wall cleaning. The barrels were abandoned when they moved away in 2015.

The individuals involved in the case are being questioned, and the case is under further investigation.

Hydrofluoric acid is a clear, volatile liquid with a pungent odor. Known in some circles as "bone-dissolving water", it can cause local burns and severe systemic poisoning.