The Texas Rangers are investigating the circumstances surrounding the death of a woman whose loved ones are questioning authorities who say the 28-year-old arrested on a traffic violation hanged herself in a Texas county jail cell.

Sandra Bland, who had ties to the Chicago area, was found dead Monday morning in a Waller County jail cell in Hempstead, about 60 miles northwest of Houston. The Harris County medical examiner has classified her death as suicide by hanging. She had been arrested Friday in Waller County on a charge of assaulting a public servant.

Trooper Erik Burse, a spokesman for the Texas Department Public Safety, told the Chicago Tribune that Bland was pulled over for failing to signal a lane change. He said she was outside the car and about to be issued a written warning when she kicked the officer and was then arrested.

Waller County District Attorney Elton Mathis, who said he had no information to think Bland's death wasn't a suicide, said Bland had traveled from Illinois to start a new job in Texas.

Mathis said the Texas Rangers would conduct a thorough investigation. He said the Rangers' arrival is "typical protocol" for when someone dies in custody.

"If I receive information that there's something nefarious going on, or foul play, we will certainly get to the bottom of that," he told the Chicago Tribune. "I understand there's some disbelief among some friends and family that she would do this to herself. That's why it's very important that the Texas Rangers be allowed to conduct a thorough investigation."

Mathis told Houston television station KPRC, "I will admit it is strange someone who had everything going for her would have taken her own life. That's why it's very important a thorough investigation is done and that we get a good picture of what Ms. Bland was going through the last four or five days of her life."

Her friends said it doesn't make sense for it to be a suicide. Bland had just accepted a job at Prairie View A&M, a historically black college in the nearby town of Prairie View. She had graduated from there in 2009.

"Anyone who knows Sandy Bland knows she has a thirst for life. She was planning for the future, and she came here to start that future, so to say she killed herself is totally absurd," friend LaVaughn Mosley told KPRC.

Another friend, Cheryl Nanton, told the Chicago television station WLS that she suspects foul play.

"I believe that we are all 100 percent in belief that she did not do harm to herself," Nanton said.

Longtime friend LaNitra Dean told WLS that Bland "was a warm, affectionate, outspoken woman" who spoke out about police brutality often on her Facebook page and was critical of injustice against blacks.

Bland's sister, Sharon Cooper, told WLS, "Each one of us feels like we lost a part of ourselves and it's hard, it's going to be hard for a very long time."