The cause of death of a 26-year-old suspect who died after Hamden police shocked him with a Taser on Saturday morning may not be determined for two months, leaving new questions about the safety of stun guns temporarily unanswered just as the New Haven Police Department prepares to deploy them in the city.

An autopsy was conducted Sunday on the suspect, David Mills, and a spokesperson for the Chief Medical Examiner’s office said a determination of Mills’ cause of death requires further studies and is not likely to be released for six to 10 weeks. Meanwhile, the Hamden Police Department is conducting an internal investigation into the death, just as it does whenever an officer uses force against a suspect, police chief Thomas Wydra said Wednesday.

“The investigation is ongoing,” he said. “I can’t comment on whether the Taser had any effect on Mr. Mills.”

Until the medical examiner releases his findings, the public should not assume that the Taser contributed to Mills’ death, Wydra said. As police attempted to apprehend him, Mills said he was high on “angel dust” and spoke incoherently, police said.

The uncertainty about the Taser’s role in Mills’ death looms as the NHPD prepares to put 50 Taser stun guns into service, part of a pilot program devised by the city’s Deadly Force Task Force and approved by the Board of Aldermen. The stun guns will be put into use once the department finalizes its policies and officers finish their training, NHPD spokeswoman Bonnie Posick said Monday.

The Hamden Police Department has used Taser stun guns for about four years, Wydra said, and the weapon has proven to be safe and effective both in reducing officer injuries and reducing injuries to those the police bring into custody.

Mills is the third Connecticut man to die in the last year after being shocked by a police stun gun. But in the two previous cases, the cause of death was determined to be the result of a drug overdose, not the Taser shock. In both cases, the cause of death took at least a month to determine.

In July, a 29-year-old died in New Britain after police used a Taser to subdue him as he resisted arrest. About two months later, the medical examiner’s office ruled the cause of death to be the result of a cocaine overdose, and an external investigation cleared police of any wrongdoing in the incident. In October, a 24-year-old Stratford man died roughly five hours after police shocked him several times, and the medical examiner ruled about a month later that the man’s death was also the result of a cocaine overdose.