TOKYO — American pole vaulter Sam Kendricks, an Olympic bronze medalist and reigning world champion, tested positive for the coronavirus and will miss the remainder of the Tokyo Games, the U.S. Olympic and Paralympic committee announced Thursday afternoon, one day before the start of the track and field competition.

Kendricks’s father and coach, Scott Kendricks, wrote in a since-deleted post on Instagram that Kendricks “feels fine and has no symptoms.” His agent, Paul Doyle, said Kendricks is completely healthy. It was not clear whether Kendricks had been vaccinated. Doyle cited privacy in declining to comment on Kendricks’s vaccination status.

“Sam feels 100 percent and in complete health,” Doyle said in a text message. “He’s in the best shape of his life. As far as Sam’s medical issues, those will remain confidential.”

Kendricks has been in Tokyo since Tuesday, according to the travel schedule he outlined in a virtual news conference last week. It is not clear how much contact Kendricks had with other athletes at the Games, but the Australian Olympic Committee said in a statement later Thursday afternoon that it briefly quarantined its entire track and field team as a precaution because of a “brief casual contact with a U.S. track and field athlete.” Three Australian athletes were tested and received negative results, and the quarantine was lifted after about two hours.

U.S. Olympic officials said they are working to gather more information. Kendricks has been transferred to a hotel and placed in isolation, the USOPC said.

“He and his close contacts were immediately notified and protocols were activated to isolate the athlete,” USA Track & Field said in a statement. “We are following the USOPC and [the Tokyo 2020 organizing committee’s] guidance on next steps to ensure the safety of the remainder of our delegation, and to offer support to Sam.”

Kendricks, a 28-year-old from Oxford, Miss., is regarded in American track and field circles as both the best pole vaulter in his generation and perhaps the nicest person in the sport. He is also a first lieutenant in the U.S. Army Reserve.

Kendricks set the American pole vault record of 6.06 meters (19 feet 6 inches) at the U.S. outdoor championships in 2019. He won the world championship months later. Kendricks finished second to Chris Nilsen at the U.S. Olympic trials, which snapped his streak of six consecutive outdoor national titles.

“He’s handling things with class as you would expect, but for sure he is disappointed,” Doyle said. “He’s a competitor and this stings for sure. He will get through it, though.”

Kendricks continued to compete internationally in the month between the U.S. trials and the Olympics, traveling to meets in Oslo and Stockholm. Last week, Kendricks said he planned to fly to Tokyo on Monday from the United States. On the Thursday before he left, Kendricks invited his hometown to watch his final pre-Olympic practice at his high school.

“I’m going to take some good time off, maybe two or three days, before I get on a plane,” Kendricks said last week. “I want to be over-rested and just a finely honed instrument is what my coach always says. Hopefully we’ll give [Sweden’s] Mondo Duplantis, the world record holder, a run for his money.”

At the 2016 Rio de Janeiro Olympics, Kendricks created one of the most memorable images of the Games. As the national anthem started playing during a medal ceremony on the other side of the stadium, Kendricks stopped mid-sprint, set down his pole and stood at attention as he looked at the U.S. flag.

“Sam is an incredible and accomplished member of Team USA and his presence will be missed,” the USOPC said in a statement. “Out of respect for his privacy, we cannot provide more information at this time.”

Roman Stubbs contributed to this report.