The Bridgeport Police Department has opened a criminal investigation into the death of Lauren Smith-Fields after the Connecticut chief medical examiner's office ruled her death an accident involving drugs and alcohol.

The 23-year-old Connecticut woman was last seen alive while on a date with a man she met on a dating app.

The ME's office said Monday that Smith-Fields died on Dec. 12 of intoxication from fentanyl combined with prescription drugs and alcohol and that her death was accidental. The Bridgeport Police Department opened a criminal investigation into her death after the autopsy report was released.

"The Bridgeport Police Department continues to treat the untimely death of Lauren Smith-Fields as an active investigation as we are now refocusing our attention and efforts to the factors that lead to her untimely death," a BPD spokesperson told Fox News Digital.

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The spokesperson added that the department has "engaged several partners to assist with this portion of the investigation." The Bridgeport Police Narcotics and Vice Division will receive assistance from the Drug Enforcement Administration in its investigation. 

Authorities found Smith-Fields in her Bridgeport apartment in December after the man she was with called police to say he awoke to find her unresponsive.

Smith-Field's death has garnered national attention in recent weeks after her family accused the Bridgeport Police Department of showing a lack of responsiveness and racial insensitivity in their handling of the investigation. Her family said police never notified them of her death, which they learned about more than a day later through a note left on her apartment door by her landlord.

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The family said police told them the man who called authorities was not a suspect in her death, but have not told them why. The detective eventually asked them to stop calling, they said. 

The family’s attorney, Darnell Crosland, said in a Tuesday statement posted to Twitter that the ME's findings do not cure the police department's "lack of process" and instead "makes it worse."

"As a result of a botched investigation this morning we are left with more questions than answers," he said.

Crosland told FOX61 Hartford that Smith-Field "didn't use drugs."

"Why is it showing drugs?" he said of the autopsy report. "Where did it come from? What was the origin of this? All we know is that a 23-year-old girl [who went] to the gym every single day doesn't use drugs."

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Crosland has notified the city of his intent to file a lawsuit accusing police of failing to properly investigate.

In his notice of intent to sue, Crosland said evidence, including a blood-stained bedsheet, was left in the apartment and was not recovered by police until two weeks later at the family’s insistence. He said that as of Friday the evidence had still not been submitted to the state forensics lab.

Bridgeport Mayor Joe Ganim said Monday that sensitivity and respect toward family members are important and the handling of the case has been referred to the Office of Internal Affairs for an investigation. He said he would work with the police chief to make changes to department practices for notifying family members of a death.

"I support and add my voice to the family, community, and elected officials who are calling for state legislation on this issue," he said.

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About 100 people held a rally in Bridgeport on Sunday — which would have been Smith-Field’s 24th birthday — asking the state take over the police investigation.

BPD offered its "sincerest condolences to the friends and family of Lauren Smith-Fields" and are asking anyone with information about her death to contact 203 576-TIPS, the spokesperson said. 

The Associated Press contributed to this report.