Partygoers probed over Sydney teen's death

Investigations are continuing into the apparent murder of a teenage boy who was one of seven people stabbed when a Sydney party turned violent.

An emotional tribute has been written by the sister of Aidan Smith, 16, who died in the early hours of Sunday after being stabbed during a fight among several young people inside a Ryde home during a birthday party.

"I love you with all my heart Aidan and I'm so sorry this had to happen to you," she wrote. "R.I.P my baby brother still cannot believe this has happened," the 21-year-old wrote on social media.

No one has been arrested or charged over the fatal stabbing rampage and several people are being questioned as investigations progress, a police spokeswoman told AAP.

Police were called to the home just after midnight and found six males, including Aidan, and a female with stab wounds.

Aidan was taken to Westmead Hospital in a critical condition but later died.

Another 16-year-old boy remains in a critical condition while a 20-year-old man who was also stabbed refused treatment.

Three other boys, two aged 16 and one aged 17, and an 18-year-old female were taken to Royal North Shore Hospital with lacerations.

Gladesville Superintendent John Duncan told reporters the matter is being treated as a homicide but could not confirm what weapon was used in the stabbings.

The fight broke out among the 50-odd partygoers.

"At this stage of our inquiries we are trying to establish why the party turned violent," Supt Duncan said.

"A number of people left the party soon after the fight broke out. Our inquiries are continuing and we hope these people will contact Crime Stoppers."