NASHVILLE, Tenn. -- Metro police said on Wednesday they are investigating a lead in a case involving a kidnapped infant and his mother who was stabbed multiple times on Tuesday.

Mom Holds Press Conference | Driver Wanted In Case | Video | Video | Images | Video

At an afternoon press conference, police said the person accused of taking the newborn on Tuesday may be in a late-model Kia Spectra with an out-of-state license plate.

Police said the vehicle pulled into the Walmart parking lot on Tuesday morning at the same time as the now 5-day-old Yair Anthony Carillo and his mother, Maria Gurrolla.

Police said the person in the Kia did not get out of the car but was parked near the family and then followed the mom and child's car onto Nolensville Road.

There is no evidence that the Kia is connected to the case, but it is a lead, according to police spokesman Don Aaron. The driver of the Kia is being pursued as a witness only.

Investigators said they are still looking for a heavyset white woman that is 5 foot 4 inches with blond hair, a ponytail and who speaks some Spanish. Aaron said he wants the public to be on the lookout for anyone who suddenly has a newborn who wasn't pregnant.

Investigators re-interviewed Gurrolla and her relatives Wednesday afternoon to see if they could recall any additional information that will help advance this case.

Abducted Infant's Mother Holds Press Conference

Gurrolla said on Wednesday that she needs her newborn son back after he was snatched from her home by a woman posing as an immigration agent.

She held a press conference Wednesday outside of Vanderbilt University Medical Center, where she is being treated for stab wounds.

Gurrolla said through an interpreter that a woman she'd never seen before showed up at her door Tuesday claiming she was an immigration agent and was going to arrest her. She said the woman stabbed her with a knife taken from her kitchen.

Gurrolla said she did not see the woman take the baby because she ran for help. When she returned, her 3-year-old daughter was in the home unharmed but the baby was gone.

Police originally said Wednesday they were questioning 30-year-old Lisa Sampson near Buffalo, N.Y., as a person of interest in the case, but now they say they don't believe Sampson was involved. She had not been arrested or charged.

The Amber Alert for the child, who was taken from his mother Tuesday afternoon, is still active.

Police spokesman Don Aaron said the infant was taken from a home on East Ridge Drive at 2:40 p.m. Tuesday.

The missing infant is Hispanic with black hair and brown eyes. At the time of the abduction, he was wearing a blue-and-white-striped onesie.

Gurrolla, was hospitalized Tuesday after suffering non-life-threatening wounds to her neck, head, thigh and breast during the abduction, police said.

The mother told police the abductor knocked on her door, claimed to be with the U.S. Immigration and Naturalization Service and wanted to see the woman's immigration papers. Gurrolla let her enter the home, which is when she was stabbed about eight times.

Neighbors said they saw a gray, two-door Honda, but police have maintained that the woman was driving a black, four-door car.

Police were going to door-to-door Wednesday and conducting interviews in the south Nashville neighborhood where the child was taken. Officers that were normally assigned to traffic patrol were helping in the investigation.

Jessenia Sigala, the cousin of Yair's father, said she was with the mother all morning and that only the immediate family had been specifically told that the baby had been born.

However, there was a blue sign in Gurrolla's front yard announcing the child's birth. Sigala said she was troubled by the sign.

If you've seen the vehicle or child, contact the Metropolitan Nashville Police Department at 615-862-8600 or Tennessee Bureau of Investigation at 1-800-TBI-FIND.