(FOX40.COM) — The Stanislaus County Sheriff’s Office is working to discover how a man ended up drowning in the Stanislaus River after his body was discovered by transients on Sunday, according to the sheriff’s office.

At 11:32 p.m., deputies arrived in the 3900 block of Topeka Street in Riverbank after calls came in from transients in the area about a possible drowning victim.

Riverbank is located about 9.5 miles northeast of Modesto.

The body was retrieved by the sheriff’s dive team and major crime unit detectives. An investigation into the “cause and manner of death” began immediately.

The man was found to be wearing clothing worn by patients admitted to a medical care facility, leading them to believe he was recently treated at a local hospital.

Investigators have yet to find any signs of trauma or injury to believe foul play is connected to the drowning.

Detectives are working with the family of the drowned man to better understand the circumstances of his death.

“Preliminary findings of a forensic autopsy suggest drowning was the cause of death,” the sheriff’s office wrote in a news release. “Additional laboratory testings through the California Department of Justice will provide more insight. Those results will not be known for quite some time, however.”