A missing 92-year-man whose car was found Thursday night near a drainage ditch in Blue Earth County may have drowned while trying to clear out a flooded culvert, authorities said Friday.

Deputies responded to the area of County Roads 32 and 144, in Pleasant Mound Township, around 6:30 p.m. Thursday after a citizen reported seeing a vehicle belonging to Marvin Borkenhagen of rural Amboy parked unoccupied near the drainage ditch, according to a news release from the Blue Earth County Sheriff’s Office.

People who know Borkenhagen told authorities that he sometimes frees ice and debris from a field culvert that feeds into the drainage ditch, and a tool he was known to use was found in the water near the culvert opening, authorities said.

A ground search was conducted Thursday night with assistance from the State Patrol helicopter.

It was suspended overnight and resumed early Friday, but as of 5 p.m., Borkenhagen had not been found.

According to authorities, the 10-yard-wide drainage ditch connects with several fields before running into Willow Creek. “The water was flowing at a steady rate during initial search efforts and was estimated to be approximately 8 feet deep,” authorities said.

Local authorities, the State Patrol and the state Department of Natural Resources will continue the search for Borkenhagen.

Although his fate is not known, the Sheriff’s Office referred to his disappearance as a “probable drowning.”