U.S. sprinter Sha’Carri Richardson, who was set for a star turn at the Tokyo Olympics this month, could miss the games after testing positive for marijuana.

Richardson, 21, won the women’s 100-meter race at the U.S. track and field trials in Oregon last month, but her positive test automatically invalidated her result in that marquee event.

The U.S. Anti-Doping Agency announced the positive test result this morning and said that Richardson had accepted a suspension of one month, starting June 28. That could clear her in time to run in the 4×100 meter relay that takes place later in the games — if she is named to the U.S. team.

In an interview with NBC today, Richardson blamed the positive test on her use of marijuana as a way to cope with the unexpected death of her biological mother while she was in Oregon for the Olympic trials. Richardson, who was raised by her grandmother, said she learned about the death from a reporter during an interview and called it triggering and “definitely nerve-shocking.”

“It sent me into a state of emotional panic,” she said. “I didn’t know how to control my emotions or deal with my emotions during that time.”

She apologized to her fans, her family and her sponsors, saying, “I greatly apologize if I let you guys down, and I did.”

USA Track & Field has notified other women who competed in the 100-meter final at the trials about the failed drug test, according to two people with direct knowledge of the information, and several runners have been told that they have moved up a spot in the final standings.

Jenna Prandini, who placed fourth at the trials, has been notified that she will now be one of the three American women running the 100 meters in Tokyo, and Gabby Thomas, who finished fifth at the trials, was named as an alternate for the race, the person said.

Richardson will be eligible to return to competition just before the track and field events at the games begin July 30. That day’s schedule includes the first qualifying rounds in the women’s 100, an event that now will happen without her.

Early Thursday afternoon, Richardson cryptically tweeted, “I am human.” And on NBC today, she expanded on that thought.

“I just say, don’t judge me and I am human — I’m you, I just happen to run a little faster,” she said, adding that she expects some people to criticize her marijuana use. “They don’t necessarily understand, and I wouldn’t even call them haters.”

While Richardson’s suspension will be over by the time the Olympic track and field competition begins, the positive test erased her Olympic trials performance in the women’s 100, meaning she will not run in the event. Unlike the Olympic selection processes of some other countries, USA Track & Field’s procedures leave little room for discretion over who qualifies. They dictate that the top three finishers in a given event at the trials qualify for the Olympics, provided their performances reach the Olympic standard.

It is possible that Richardson could still compete in the 4×100-meter relay even if she is ruled out of the individual race. The decision would be up to USA Track & Field, the national governing body of the sport.

Up to six athletes are selected for the country’s relay pool, and four of them must be the top three finishers in the 100 meters at the Olympic trials and the alternate. The governing body names the remaining two members of the relay pool.

In a statement, USA Track & Field said Richardson’s situation “is incredibly unfortunate and devastating for everyone involved,” but made no mention of whether or how she would compete at the Olympics.

Renaldo Nehemiah, Richardson’s agent, did not respond Thursday to a phone call or a text message.

Marijuana is on the World Anti-Doping Agency’s list of prohibited substances. Both USADA and the United States Olympic & Paralympic Committee are signatories to the WADA code, meaning they follow its rules.

“While we are heartbroken, the USOPC is steadfast in its commitment to clean competition and it supports the anti-doping code,” the organization said in a statement this morning. “A positive test for any banned substance comes with consequences and we are working with the USATF to determine the appropriate next steps. We are dedicated to providing Sha’Carri the support services she needs during this difficult time.”

Marijuana is banned only during in-competition periods, which are defined as beginning at 11:59 p.m. on the day before a competition and ending at its conclusion. Athletes may have up to 150 nanograms per milliliter of THC, the main psychoactive substance in marijuana, without causing a positive test.

According to USADA, marijuana is a prohibited substance because it can enhance performance, it poses a health risk to athletes and its use violates the spirit of the sport.

“The rules are clear, but this is heartbreaking on many levels; hopefully, her acceptance of responsibility and apology will be an important example to us all that we can successfully overcome our regrettable decisions, despite the costly consequences of this one to her,” Travis Tygart, CEO of USADA, said today in an emailed statement.

A suspension for testing positive for marijuana can be up to two years. The minimum length is a month, if an athlete can prove the use of marijuana was not related to sports performance and if the person completes a substance abuse treatment program. Just last month, USADA suspended Kahmari Montgomery, a sprinter, for one month after he tested positive for marijuana.

Richardson’s positive test came about a week before the U.S. Olympic & Paralympic Committee needs to submit the names of its athletes competing in Tokyo. And Richardson was not only supposed to be one of them but also was expected to be one of the most recognizable Olympians, at least by the end of the Games.

She dominated the opening weekend of the trials, drawing attention for her scintillating performances, her long orange hair (“to make sure that I’m visible and being seen,” she said) and an emotional moment when she sprinted into the stands to hug her grandmother.

Her victory in 10.86 seconds made her an instant favorite to win the gold medal in Tokyo and set up a highly anticipated showdown at the Olympics with Jamaican sprinter Shelly-Ann Fraser-Pryce, who won the 100 at the last world championships. Richardson ran the second-fastest 100 this year, behind Fraser-Pryce, and in April ran the sixth-fastest time ever.

“This will be the last time the U.S. doesn’t come home with a gold medal in the 100,” Richardson said to NBC.