A Centers for Disease Control and Prevention researcher has been found dead, seven weeks after he left the agency's headquarters in Atlanta and mysteriously vanished without a trace.

Officials said a body was recovered Tuesday from the bank of the Chattahoochee River in Atlanta and that they have positively identified the deceased person as 35-year-old Timothy Cunningham.

Authorities said that there was no indication that there had been foul play, however, the circumstances surrounding Cunningham's death are still largely a mystery.

Authorities said during a news conference Thursday that it appears Cunningham drowned, but they have not yet determined whether his drowning was accidental or intentional.

“Barring some new information coming forward,” Atlanta police Maj. Michael O'Connor told reporters, “we may never be able to tell you how he got into the river.”

Cunningham, an epidemiologist, disappeared on Feb. 12, not long after learning why he had been passed over for a promotion. Authorities said he told colleagues that he was not well, then headed home early from work.

Since then, Cunningham's family had been pleading for answers, partnering with Atlanta CrimeStoppers to offer a $10,000 reward for information leading to Cunningham's return.

“Tim is a very loving, brilliant, and responsible young man,” according to a GoFundMe page. “Therefore, his sudden disappearance is highly irregular and very much out of character for him. His friends, family, and colleagues are desperately searching for him. We are launching this fundraising campaign to collect funds that will be used to establish a reward for information that will help locate Tim.”

Search-and-rescue crews had been scouring nearby woods, canvassing hospitals and jails, reviewing cellphone records, searching cemeteries and even flying over the immediate area with a helicopter looking for signs of life — or worse. Authorities said Thursday that they had searched the river back in February but had not found any indication that there was a body.

They responded Tuesday night to reports that a body had been spotted by the river and found Cunningham lying face-up on the muddy bank.

Police said Cunningham, who was known as a jogger, was wearing his favorite jogging shoes when he was found. He had three crystals in one of his pockets, police said, noting that he was a collector.

O'Connor, commander of the police department's major crimes division, told reporters that during the course of the investigation, detectives interviewed family members, friends and colleagues and looked at many other factors — none of which showed any indication that there had been foul play. O'Connor said that although authorities are still awaiting toxicology results and for the medical examiner's report to be finalized, investigators believe that Cunningham drowned.

However, O'Connor said that the case is still under investigation.

“Things are fluid,” he told the reporters, “and things can change.”

Following the news of Cunningham's death, a spokeswoman for the CDC said that his colleagues and friends at the agency are “deeply saddened to learn of his death.”

“Tim was a treasured member of the CDC family and his work as an epidemiologist was invaluable to CDC’s efforts to protect the health, safety, and security of Americans,” the CDC said in a statement Thursday to The Washington Post.

“Tim was a team lead in the Epidemiology and Surveillance Branch of CDC’s Division of Population Health. He also completed CDC’s Epidemic Intelligence Service Officer program. His research has been oriented towards understanding health differences related to race/ethnicity, socioeconomic status, gender, and geography. CDR Cunningham also deployed for numerous public health emergency responses, including Superstorm Sandy, Ebola, and Zika. He served in multiple leadership roles with the Atlanta Commissioned Officers Association.

“Tim’s impact will be felt not only through his significant contributions to CDC’s mission, but also through his influence on the lives of his colleagues and friends. We extend our condolences to his family and loved ones during this difficult time.”

About a week before his disappearance, Cunningham was told by his CDC supervisor that he would not get a promotion. The explanation was given to him on Feb. 12 — the Monday he went missing.

O'Connor, with the Atlanta Police Department, previously said that authorities do not know why Cunningham was denied the promotion. The CDC did not respond to a request for an explanation.

But Cunningham, who told co-workers that he was “upset” about the decision, left work soon after learning the news, saying he was not feeling well, O'Connor said. He added that Cunningham had also called in sick the two previous workdays on Feb. 8 and 9.

O'Connor previously stressed that investigators have not uncovered any evidence that Cunningham's promotion snub was directly linked to his disappearance. The CDC did not identify any problems with his job performance or workplace issues beyond the promotion denial, O'Connor said.

“We're open to any and all possibilities,” O'Connor said during the investigation, though he declined to say how investigators were taking Cunningham's mental health into account during the search.

Cunningham's work at the CDC fueled speculation and conspiracy theories about his disappearance, including one dubious story on a website that said Cunningham disappeared amid warnings that his patients were dying from botched flu vaccines.

But Cunningham worked in the CDC's chronic disease unit, not in the section that deals with infectious disease, according to authorities.

“He had no access to classified material,” O'Connor previously told reporters. “He would not be of the type of person that, if you kidnapped him and held him, he could give you access to some horrific virus that could be a real problem for all the rest of us.”

The incident took other bizarre turns, too.

Viviana Tory, a neighbor of Cunningham's, reported an odd encounter between her husband and Cunningham the day before he disappeared.

“He told my husband to tell his wife — me — to erase his cellphone number from my cellphone,” she told CBS News.

O'Connor confirmed the claim and told reporters that he would follow up on it, but he had few details about its significance. When asked about the claim, police spokesman D.T. Hannah told The Post that no further information was available.

“The most unusual factor in this case is that every single belonging that we are aware of was located in the residence,” O'Connor had told reporters. “His keys, his cellphone, credit cards, debit cards, wallet, all of his identification, passports. Anything you could think of, we've been able to locate. None of those items are missing.”

Cunningham had no Uber or Lyft transactions that day, and his car and dog, Mr. Bojangles, were found at his home, O'Connor added.

Cunningham's father, Terrell, told the New York Times that he had concerns after recent interactions with his son, whom he described as focused on a host of professional and personal issues.

“The tone and the numerous exchanges gave us reason to be concerned about Tim,” he told the newspaper. “And I don’t know if it’s an instinct you have because it’s your child, but it was not a normal conversation, and I was not comfortable.”

Cunningham's parents were notified by police about four bodies found as part of the search, only to be told later that none of them was of their son.

“It takes you to a place that the light is not shining in,” Terrell Cunningham told CNN. The family has not responded to numerous requests for comment from The Post.

Tim Cunningham had been a prominent fixture in the Atlanta community. In an Atlanta Business Chronicle 40 Under 40 Awards profile last year, Cunningham said he was “using the skills I have to improve and help the lives of others,” referring to his work at the CDC.

The article said he was continuing on his family's path into the medical field; his father was an Air Force nurse for 30 years and his mother worked for the state health department as a program manager.

This post has been updated.