Missing grad student Jelani Day died from drowning, coroner says. It's still unclear how he ended up in the Illinois River.

• Jelani Day went missing in August. His body was found nine days later floating in the Illinois River.
• On Monday, the county coroner determined that Day's cause of death was drowning.

Jelani Day, a missing grad student whose body was found floating in the Illinois River last month, died of drowning, the local coroner said Monday. But it's still unknown how Day came to enter the river.

Day's case gained national attention when his family started to complain publicly that investigators were pushing a suicide narrative for the 25-year-old's death, who they felt had no reason to kill himself.

In an interview with Insider earlier this month, Day's brother Seve said he viewed the body and wasn't convinced it's his brother, since it had decomposed past all recognition.

In a statement on Monday, LaSalle County Coroner Richard Ploch explained that there's no specific test to determine if someone has died of drowning, and that it's a conclusion forensic pathologists come to after excluding other options.

Ploch pointed out that there were challenges in conducting an examination due to the the state the body was in. He said that there was no evidence to suggest a different cause of death, however.

"Although the examination was suboptimal based upon the degree of decomposition and predation activity while the body was within the river during a period of warm weather, there was no evidence of any antemortem injury, such as manual strangulation, an assault or altercation, sharp, blunt, or gunshot injury, infection, tumor, natural disease, congenital abnormality, or significant drug intoxication," Ploch said in the statement.

"The manner in which Mr. Day went into the Illinois River is currently unknown," he added.

Ploch said his office would no longer be commenting on the case, out of respect for the family.

Meanwhile, Day's mother, Carmen Bolden Day, publicly spoke out against the coroner's findings on Monday, saying she still believes that her son was murdered.

"That is a narrative that my son did something to himself. He did not," Day said at a general assembly meeting of Illinois State University's Black Student Union, according to CNN.

"Somebody did this to him, and they are going to be held responsible for doing what they did to my son," she added.

Insider reached out to the family for comment on Tuesday, but did not immediately receive a response.