A search for a missing woman is continuing Thursday. Police say Lisa Gibson, 32, is a "person of interest" after the deaths of her two children on Wednesday.

An infant and toddler were rushed to hospital in critical condition but couldn't be revived.

Police say Gibson was the last person to see the kids.

"At this point, we are concerned for her well-being. We want to make sure that she's fine and obviously, once located safely, we'll be looking to speak with her regarding the incident," said Const. Eric Hofley.

Officers were called around 8 a.m. Wednesday morning to the first 100 block of Coleridge Park Drive in  Westwood.

Neighbours said the children were found in a bathtub by their grandma.

Someone at the home called 911.

Police have not confirmed how the children died.

"I just heard there was a tragedy in the neighbourhood and some children were hurt," said one neighbour.

"Our daughter met Lisa and her baby because they had babies in common. Just a beautiful family as far as we knew," said Earl Gould, another neighbour.

Gibson, who worked at a hospital pharmacy and her husband, an electrician, were often seen outside with their two-year-old daughter and infant son, said residents.

Neighbours said Gibson had been taking medication for postpartum depression and the children's grandparents had been visiting the home daily to help.

Officers remained on scene hours after being called to the house, with several units searching the area.

Wednesday evening, search and rescue crews combed the Assiniboine River near the home and looked into nearby vehicles until skies grew dark. The Air1 helicopter continued to circle above after nightfall.

People who didn't know the family arrived at the scene to lay flowers and teddy bears and light candles at a growing memorial.

Jolaine Vandal came from Charleswood to pay her respects. Fighting back tears, she told CTV News, "Being a mother of three myself, this is really hard."

Thursday afternoon, the police dive team and river patrol boat went up the Assiniboine River as they continued their search.

Anyone with information on Lisa Gibson's location is asked to call investigators at 204-986-6508 or Crime Stoppers at 204-786-8477.

A vigil for the Gibson family was also scheduled to be held at 7 p.m. on July 25 at Winnipeg Mennonite Elementary, 250 Bedson Street.

- with a report from Alesia Fieldberg and files from the Canadian Press