For three miles, the Toyota SUV rumbled from Chinatown to Dorchester with a middle-aged woman trapped beneath its chassis, her legs sticking out from under the car. Her screams pierced the early morning stillness so loudly that one witness initially thought it was a car alarm, police said.

But driver Xiao Ying Zhou said she did not hear or see the woman and could not understand why her 2015 RAV4 seemed to be driving raggedly as she left Chinatown and headed down the interstate Monday morning, according to her lawyer.

The woman, miraculously, was still alive Monday evening, but had sustained traumatic injuries, according to authorities.

At an arraignment in Boston Municipal Court, Zhou pleaded not guilty to charges of assault and battery with a dangerous weapon and leaving the scene of an accident, and was ordered held on $5,000 bail.

Her lawyer acknowledged that Zhou, a 45-year-old who recently moved from Chinatown to Cape Cod, trapped and dragged the woman, but said she did so unwittingly and tried to help the woman as soon as she realized.

“She is innocent, according to what she told me,’’ her court-appointed lawyer, Jose A. Vincenty, told reporters after the arraignment. “She was driving, thought the car was operating in a strange way; she pulled out at the exit and at that particular point in time saw the person and tried to assist.’’

Authorities painted a different picture, saying that Zhou initially stopped after she had dragged the woman 2.5 miles. After looking under her SUV, she immediately got back into her car and sped away, according to an eyewitness account.

Zhou continued driving nearly three-quarters of a mile farther with the woman still trapped underneath, while at least one witness followed her and police eventually found her on Columbia Road in Dorchester, according to prosecutors and a Boston police report.

The ghastly incident began a little before 1:40 a.m. when Zhou struck a 56-year-old man and his 48-year-old wife as they crossed the road near the intersection of Kneeland Street and Harrison Avenue in Chinatown, police said. Emergency responders treated the man for lesser injuries, but his wife was gone — dragged away by the SUV.

Zhou then turned onto the ramp for Interstate 93, drove south on the highway for nearly two miles, and got off at Exit 15, where she pulled over in the rotary at Columbia Road and Morrissey Boulevard, Assistant District Attorney Kristina Kerwin said in court.

According to a witness, Zhou checked under the car and then headed down Columbia Road all the way to Boston Street, where pursuing witnesses and then police caught up with her, Kerwin said.

“The victim is in very critical condition,’’ she said. Kerwin sought $7,500 bail and multiple conditions, including that Zhou be barred from driving and turn over her passport.

The prosecutor said doctors managed to save the woman’s arms, but she underscored the horror of the experience.

“A witness heard what he believed to be a car alarm . . . that turned out to be the victim screaming,’’ Kerwin said. “Multiple witnesses did see the victim’s legs poking out from underneath the car during [Zhou’s] path of flight.’’

During her 15-minute arraignment, Zhou hid her face with a black jacket.

“She wants to have a fair and impartial trial and not a trial by the media,’’ Vincenty said in court. He asked Judge Tracy-Lee Lyons to release Zhou on personal recognizance.

Vincenty argued that Zhou was not a flight risk and had always shown up at hearings in previous court cases. He reiterated that she immediately tried to help the injured woman — and scraped her own arms trying to free her — once she realized what she had done.

The judge set bail at $5,000 and agreed to conditions sought by the prosecutor, including a request that any blood drawn during treatment of Zhou’s injured arms at Boston Medical Center be kept as potential evidence.

After the hearing, Vincenty said Zhou told him that another car had been ahead of her in Chinatown, “so it’s possible the other car hit these two individuals and unfortunately the other woman must have been dragged from my client’s car.’’

Zhou, who has lived in Massachusetts for the past decade, runs a massage business, according to police and state records. She received her driving license only last fall, according to the Registry of Motor Vehicles. She has had at least two previous criminal cases against her, a law enforcement official said.

In 2007 and again in 2009, she was charged with sexual conduct for a fee; each time she received a “continuance without a finding,’’ meaning she acknowledged there was sufficient evidence to convict her while avoiding a formal guilty finding. The official asked not to be named because he was not authorized to discuss Zhou’s criminal history.

A woman who was riding in a car on Columbia Road in Dorchester early Monday told the Globe she saw what she thought was an animal trapped in the undercarriage of the white SUV when it pulled beside her.

“It was like an animal or a big bag, just something weird under the car,’’ Elizabeth Amas said in a telephone interview.

She heard a man trailing the SUV repeatedly honk his horn, she said. When the RAV4 finally pulled over, Amas shuddered at the realization that it actually had been a person trapped under the vehicle all along.

“It was horrible,’’ she said.

Amas, who called police, said rescuers were not able to free the woman until a tow truck came and lifted the car off of her.

Eric Moskowitz can be reached at eric.moskowitz@globe.com. Follow him on Twitter @GlobeMoskowitz. John R. Ellement can be reached at ellement@globe.com. Follow him on Twitter @JREbosglobe.