The 71-year-old “had not been seen or heard from in several days” when police visited his home on Monday morning, the Hawaii Police Department said.
Officers found the man approximately 22 feet beneath the ground and said in a report “it appeared that he had fallen through a soft area of ground into a lava tube on his property”.
Lava flows through natural “tubes” consisting of underground tunnels found across Hawaii in the aftermath of a volcanic eruption. The conduits, which form under the hardened lava flow, can reportedly be found miles from the eruption site.
Lava tubes can effectively turn into long, narrow caves once the conduit becomes “extinct” and the rocks cool off after the lava stops flowing.
A rescue team with the Hawaii Fire Department managed to extract the man’s body from the bottom of the lava tube.
He was then transported to a local medical centre, where he was pronounced dead.
Police have not yet released the identity of the man, pending the notification of his next of kin.
An autopsy report indicated he “died as a result of injuries consistent with falling”, police said in the report published on Wednesday.
Officials also said that, while “no foul play is suspected in this case”, the police department’s criminal investigation unit was investigating the incident.
Hawaii Police Department Major Robert Wagner told local news outlet Big Island Now that the lava tube was about two feet wide and 25 feet deep.
The victim died after he “fell about 20 feet down”, Mr Wagner told the outlet.