A 52-year old man has been arrested for his alleged involvement in an acid case which burnt the left buttock of a nurse, police said on Monday.
Investigations against him are ongoing.
Ms Wan Zahfirah Arshad, 24, had sat on an MRT priority seat last Thursday from Woodlands station. She felt some wetness and an unbearable stinging sensation, and later realised she had been burnt by a corrosive substance.
The Straits Times understands it was sulphuric acid.
The police said they managed to identify the suspect with the help of CCTV footage. His whereabouts were located, and the man was arrested yesterday night.
The incident involving the nurse follows two other cases in which people suffered burns after sitting on corrosive substances in public transport areas.
The police has said the cases may be linked.