WITI-TV, MILWAUKEE - Authorities say they have found a 6-week-old boy whose mother and two young siblings were found dead after a fire in their home, as well as a 20-year-old woman who lived at the residence. The infant was safe inside of a baby carrier outside of a northside Milwaukee church.

Police were treating the deaths of the 24-year-old Rachel Thompson, 4-year-old Torian Thompson-Carter and 3-year-old Jaden Thompson-Carter as homicides, Milwaukee Police Capt. Kurt Leibold said. Their bodies were found after a fire at their home that was reported early Friday.

Investigators are now looking for Brittney Robertson, a woman who lived at the home, police spokeswoman Anne Schwartz said in a statement.

"We are currently unable to locate her and are concerned for her safety," Schwartz said.

When asked whether Robertson was considered a suspect, Schwartz said Robertson was "a critical missing person."

Police were unable to issue an Amber Alert because they didn't have enough information for one, Leibold said.

"The criteria isn't matching because we do not have a person to name or a possible vehicle the boy is in," he said.

Three people who lived downstairs from the family escaped the fire.

If you have any information that can help police in this case, you're urged to call 414-935-7360.

Monitor FOX6 News and FOX6Now.com for updates on this developing story.