A total of five North Korea players have tested positive for steroids at the women's World Cup in football's biggest doping scandal for almost two decades.
FIFA President Sepp Blatter said on Saturday that after two players were caught during the tournament earlier this month, FIFA tested the rest of the North Korean squad and found three more positive results.
"This is a shock," Blatter told a news conference. "We are confronted with a very, very bad case of doping and it hurts."
The last doping case at a major event came at the men's 1994 World Cup in the United States, when Diego Maradona was kicked out after testing positive for stimulants.
Colombia's reserve goalkeeper Yineth Varon has meanwhile been suspended for failing an out-of-competition test just before the World Cup in the wake of undergoing hormonal treatment.
FIFA has already met with a North Korean delegation and heard arguments that the steroids were accidentally taken with traditional Chinese medicines based on musk deer glands to treat players who had been struck by lightning on June 8 during a training camp.
The case will now be taken up by FIFA's disciplinary committee.
Blatter said the North Korean federation "wrote to us and they presented their excuses. They said that a lightning strike was responsible for this."
Defenders Song Jong Sun and Jong Pok Sim tested positive for steroids after North Korea's first two group games and were suspended for the last match. The team was eliminated in the first round after losses to the United States and Sweden and a draw with Colombia.
The names of the three other players would only be made public at a later stage, FIFA said.
The gland in question comes from musk deer living in a large swathe of Asia from Siberia to North Korea. The hairy 4-centimeter gland is usually cut open to extract a liquid which is then used for medical purposes.
Doping officials have been concerned about such naturally-occurring substances in recent years. During the run-up to the 2010 World Cup in South Africa, FIFA's concernes focused on African plants that could players an unfair advantage by providing energy boosts or helping to heal muscle injuries.
FIFA investigators who discovered evidence of doping in the North Korean samples found themselves in uncharted territory as such steroids had not been encountered before. Experts from the World Anti-Doping Agency were called in to confirm the breach of doping rules.
"It was very complex," FIFA's chief medical officer Jiri Dvorak said. He added that the medical officer of the North Korea team provided a sample of the medicine to help their analysis.
The musk gland extract "it is not part of the world of doping," Dvorak said. "It is really the first case in which this has been discovered."
The North Koreans first mentioned the lightning incident after losing their opening match to the United States. When North Korean officials were asked later, they refused to elaborate on the circumstances.
Dvorak also said the information was still sketchy. "We saw some pictures with ambulances and saw that some players were taken from the pitch, but that is all we have," he said.
FIFA also got information from North Korea about the treatment of the players and "this very first report did not include the traditional Chinese medicine," Dvorak said.
The tournament ends on Sunday with the final between the United States and Japan.