Lewiston police say the investigation into the death of a toddler who was struck and killed by her mother’s SUV while attending her sister’s 10th birthday party celebration Saturday evening could take several days or possibly weeks to complete.

Lt. David St. Pierre, spokesman for the Lewiston Police Department, said Sunday evening that investigating officers subjected the little girl’s mother, Taneisha Thomas, 27, of 50 Fairmount St., to a blood test following the accident outside Thomas’ apartment at the Pleasant View Acres housing complex.

According to records from the Maine State Bureau of Identification, Thomas was convicted of operating under the influence in 2013 and is facing a recent charge of OUI. Thomas was driving with a conditional license when she struck and killed her daughter.

St. Pierre said police are still interviewing witnesses. Police say they believe that Thomas was backing up when her 2004 Mercury Mountaineer struck her 17-month-old daughter, Tiannah Sevey, about 5 p.m. Saturday. The child was treated at the scene and taken to Central Maine Medical Center in Lewiston, where she died.

“This is going to be a long investigation,” St. Pierre said. “We still have a long ways to go.”

The blood test the mother underwent is standard in fatal motor vehicle crashes. It is given to determine whether the driver was under the influence of drugs or alcohol. The results from the test of Thomas could take several weeks to process, St. Pierre said.

No charges have been filed, St. Pierre said, but the Maine Attorney General’s Office and the Maine Department of Health and Human Services have been notified. In cases where there are other children in a home, it would be up to the DHHS to determine if they should be removed. It is standard procedure to notify the AG’s Office whenever there is a death of a child under the age of 3.

Lewiston police confirmed Sunday evening that the victim had at least two other siblings, a 10-year-old sister and a 4-year-old sister.

A makeshift memorial stands for 17-month old Tiannah Sevey who was killed when her mother, Taneisha Thomas, ran her over. Staff photo by Jill Brady

“Any fatal or major event that could result in criminal charges is when we want to keep everyone on board with the investigation,” St. Pierre said when asked why those agencies were being kept in the loop.

Lt. Mike McGonagle of the Lewiston Police Department responded to the tragic accident Saturday night and spoke with the little girl’s mother, who told him that family and friends had gathered at her home to celebrate her 10-year-old daughter’s birthday.

McGonagle said he is not sure how many children attended the party, which included Tiannah Sevey’s 4-year-old sister.

McGonagle said Lewiston police officers performed CPR on Tiannah, but she died later at Central Maine Medical Center.

The Sun Journal newspaper, citing state records, reported that Thomas’ license was suspended on Aug. 17 after she was charged with OUI with a prior OUI conviction and operating without a license on Aug. 13 on Turner Street in Auburn. The suspension was stayed on Sept. 11 and she was operating with a conditional license, which expires Oct. 7.

She is scheduled for a hearing on the license suspension on Thursday.

Thomas was convicted of OUI in 2013 after striking a parked car in front of her home on Fairmount Street. Her blood alcohol level at the time was 0.27 percent, more than three times the legal limit. She was driving a 2000 Subaru owned by Michael Sevey and strayed to the right of the road, striking the car, according to the accident report. The impact forced the parked car into two other parked vehicles.

Thomas also had a conviction for theft by unauthorized taking in 2011.

On Sunday morning, family members, neighbors and members of the community set up a memorial next to the parking lot where the toddler was killed. There were stuffed animals, flowers, candles, money, balloons, a Red Sox cap and a rosary. Someone taped a photograph of Tiannah to a telephone pole, the Sun Journal reported.

A small sign that read “R.I.P. T.T. – An angel is never forgotten” was taped to the pole.

A child who stopped by the memorial Sunday evening said he cried in his sleep and another child asked a man why people had been stopping by the memorial all day.

“That’s because there is so much love for one little girl,” the man replied.