The cause of Jimmy Hayes’ death remained unclear even after an autopsy of the former NHL player, a spokesman for the Massachusetts medical examiner’s office told The Post on Wednesday.

Toxicology testing is underway to help determine the cause of death, though the results could take up to several weeks, the spokesman said.

Hayes, a Dorchester, Mass. native who won a national championship at Boston College and later played for the Bruins, died unexpectedly Monday morning in his home outside Boston.

He was 31.

It is not uncommon for an autopsy report to not yield a cause of death, particularly in the case of a former athlete as young as Hayes, according to the spokesman.

The autopsy was conducted by a pathologist.

Known for his fun-loving personality and smooth hands around the net, the 6-foot-5, 215-pound forward played for the Blackhawks, Panthers, Bruins and Devils across seven NHL seasons.

He last appeared in a professional game in the 2018-19 season as a member of the minor league affiliate of the Penguins.

Following his playing days, Hayes co-hosted a hockey and lifestyle podcast.

He is survived by his wife, Kristen; two young sons, Beau and Mac; parents, Shelagh and Kevin Sr.; and siblings, Genevieve, Eileen, Justine and Kevin, who currently plays for the Flyers and spent five seasons with the Rangers.