Authorities say it could be weeks before it is known what killed a man who died Sunday morning after a struggle with St. Paul police.

Officers responding to a call about a suicidal man on drugs reportedly sprayed Joseph Kubat, 21, with a chemical irritant -- to no effect -- then shot him with a Taser.

Once handcuffed, Kubat became unresponsive, police spokesman Peter Panos said, and despite efforts to revive him, he died at the scene.

On Monday, Don Gorrie, a spokesman for the Ramsey County medical examiner's office, said that a cause of death cannot be determined until after toxicology results are complete, and that "can take weeks." No preliminary information was available.

In an interview late Sunday, Kubat's mother, Denise Chapman of Chaska, said that her son was not suicidal and that she believed he'd taken the hallucinogen LSD.

Tasers and drugs have proven a fatal combination in two other Minnesota cases that ultimately found cocaine intoxication or delirium to be the overriding factors in the deaths. One of those cases occurred a few years ago in St. Paul.

Three years ago, in Nashville, Tenn., a 21-year-old man who had marijuana and LSD in his system died after being shocked by a Taser up to 19 times. An autopsy found he died as result of "excited delirium," caused by extreme agitation and drug use.

Panos said Monday that he did not know how many times the Taser was used on Kubat.

Asked whether the department, now witness to a second Taser-related death, might rethink its Taser policy, Panos said: "We'll see what comes out of the investigation first."

The officers involved in Sunday's incident -- Christopher Hoyt, Adam Bailey and Susan Hartnett, all of the Eastern District -- are on three-day administrative leave.

Librarian Roberta Hovde contributed to this report. Anthony Lonetree • 651-298-1545