Police are seeking information from the public as they investigate the circumstances surrounding the death of an 18-month-old girl.

Comfort Joy Witeri-Thompson died late on Tuesday night at Waikato Hospital, and a post-mortem is underway, says Detective Senior Sergeant Matt Cranshaw.

"While Comfort's injuries are believed to be non-accidental, police are still in the process of identifying what occurred at a Tirau address leading up to Comfort requiring medical assistance.

"We would ask that anyone with information relating to the girl's death to please contact Tokoroa Police on (07) 885 0100."

Alternatively, information can be given anonymously via the Crimestoppers 0800 555 111 line.