A 29-year-old man has been arrested after his 19-year-old sister was found motionless and subsequently pronounced dead in a residential unit along Clementi West Street 1.

The man was arrested for voluntarily causing grievous hurt.

The police were alerted on Wednesday, May 5 at about 6.30am to a case of unnatural death at a residential unit.

The woman was already lying motionless in the unit when officers arrived.

The police said: "The woman was pronounced dead at scene."

The man is the biological brother of the deceased, preliminary investigations revealed, according to the police.

Investigations are ongoing.

The man will be charged in court on May 6.

If convicted of voluntarily causing grievous hurt, he can be jailed up to 10 years and fined or caned.