Two dead after collapsing at Sydney dance music festival Defqon.1

A man and woman have died and a further two people remain in hospital in a critical condition following a dance music festival in Sydney's west.

The 23-year-old man and 21-year-old woman collapsed at Defqon.1 festival in Penrith about 9pm on Saturday, and were rushed to Napean Hospital. Medical staff were unable to save them and they died a short time after.

A 26-year-old Jamisontown woman was also rushed to the hospital where she remains in a critical condition. A 19-year-old man from Artarmon was airlifted to Westmead Hospital in a critical condition and remains in intensive care.

Emergency services attending the Sydney International Regatta Centre responded to multiple reports of suspected drug overdoses.

Police have been told an additional 13 people attended Nepean Hospital for treatment for drug-related issues, while as many as 700 people sought assistance from medical staff on-site.

Ten charged with drug supply offences

Ten people were charged with drug supply offences following the festival, with three due to appear in court on Sunday.

A range of illicit drugs were seized including MDMA, cocaine and ecstasy.

NSW police conducted 355 drug searches leading to 69 people found to be in possession of drugs, including the 10 charged with supply offences.

7 News / Newshub.