Two 23-month-old toddlers remain in a critical condition after being found unconscious in a swimming pool at a home in Sydney’s north west.

The twins were unresponsive after they were pulled from the backyard pool of a home in Charbel Place at Kellyville Ridge about 7pm on Tuesday.

Paramedics said the girl and boy were treated at the scene by NSW paramedics before being taken to Westmead Children’s Hospital with a police escort.

Chief Inspector Garry Sims said police believed the children were out of the sight of their parents for a period of time.

“I think those with children are very aware how quickly things can change,” he said.

“Whatever happens in seconds is a life-changing situation for the families, and you can’t imagine the grief the family are going through.”

“Obviously at this time of year we urge people to be very vigilant around swimming pools, maintain the security and keep an eye on the children.

“Our thoughts and prayers are with the family for the tragic incident.”

He said the pool met all safety requirements.

Officers from Blacktown Local Area Command are investigating the circumstances surrounding the incident.