A one-year-old child has died after being found unconscious at a home in Sydney’s west.

Emergency crews were called to O’Hagon Street in Chester Hill about 3.30pm on Sunday.

NSW Police said the baby boy was found unresponsive and paramedics were not able to revive him.

“The cause of death is yet to be determined,” they said in a statement.

Paramedics and police attend a Chester Hill street where the child was found unresponsive. Photo: ABC News

Officers have spoken with distraught witnesses at the scene, including a woman who was loaded into an ambulance on a stretcher.

A family friend said the infant was a twin.

“[It’s a] very close family,” she said.

“The two twins were always together – always together.”

The woman said the boy’s mother was a good parent with six children.

“I’m in shock, disbelief, heartbroken,” she added.

“I just can’t believe this has happened.”

–ABC