Texas police are asking for the public's help in locating a mother and her infant daughter who went missing after dropping an older child off at school last week.
Austin resident Heidi Broussard, 33, and her 3-week-old daughter, Margot Carey, were last seen Thursday morning as Broussard dropped off the couple's 6-year-old son at the Cowan Elementary School, according to the Austin Police Department. Their last known location is believed to be their apartment complex near West William Cannon Drive and South First Street after they left the school, Austin Police Det. Brad Herries told reporters at a news conference Tuesday afternoon.
Broussard was reported missing around 7:30 p.m. that night, Herries said.
The mother and daughter are presumed to be alive, and police have not named a person of interest in their disappearance, Herries said.
"Our assumption is that they are alive, and the sooner that we can find them the better," he said.
Broussard's fiance, Shane Carey, described her to ABC News as an "amazing mom" who "would never disappear."
The couple have two children together and are also raising an older child from Carey's previous marriage, he said.
Broussard's wallet and purse were left inside her unlocked car at their home, while Margot's diaper bag was inside the apartment, Carey said.
There was no sign of forced entry in the apartment, and nothing of value was missing, he added.
Carey pleaded with whoever may have Broussard to return her and his daughter home safely.
"Drop her off anywhere -- I don't care," he said through tears. "Just make sure she's safe and OK, the baby's OK."
Broussard is described as a white female, about 5-foot-3-inches tall and 150 pounds with long, dark hair and highlights. She is believed to have been wearing a purple long-sleeve shirt at the time of her disappearance, police said.
Margot weighed just 7 pounds and 7 ounces at the time of her last doctor's appointment. The clothing she was wearing at the time of her disappearance is not known.
Investigators are asking for the public to continue to submit tips to find Broussard and Margot.
The Texas Department of Public Safety, FBI, Texas Rangers and Texas Parks & Wildlife Department are assisting in the investigation.
ABC News' Sabina Ghebremedhin contributed to this report.