More than 100 players at the FIFA Under-17 World Cup in Mexico this summer tested positive for banned drug clenbuterol due to contaminated meat, the world governing body has revealed.
FIFA's chief medical officer Jiri Dvorak revealed last night that players from 19 of the 24 squads involved, in roughly equal numbers, had shown traces of the substance after analysis of urine samples.
However, Dvorak insisted there had been no harm to the players exposed to the contaminated food in June.
Dvorak would not say whether England's Under-17 squad was one of those involved.
He said: "FIFA was very alarmed and it was highly surprising to see something like this - I had not seen anything like it in my 20 years in this post.
"My first question was, 'Could any harm have been done to the players?' and I was assured by the different medical specialists the answer is no."
Dvorak said that as early as April the German anti-doping organisation had issued a warning that athletes should exercise caution in Mexico and China because of adverse analytical findings due to meat contamination.
FIFA ordered meat samples to be collected from team hotels and 30% of these showed the presence of clenbuterol.
The Mexican government have made a number of arrests and closed down several slaughterhouses in recent weeks after being alerted to the issue, according to Mikel Arriola, an official from Mexico's health ministry.
Mexico's victorious Under-17 team did not have a single adverse finding; after the positive tests for the senior players they were only allowed to eat fish and vegetables.
Positive tests for five players from the senior Mexico squad had alerted FIFA to a possible issue, and when four more positive tests emerged from the youth tournament the governing body decided to reanalyse all the 208 urine samples taken.
A laboratory in Cologne discovered the presence of the steroid in 109 of those samples - 52.4%.
Clenbuterol is banned in farming in most countries but is used to speed up growth and increase muscle mass in cattle.
In cycling, Tour de France champion Alberto Contador is going to the Court of Arbitration for Sport claiming his positive doping test for clenbuterol is due to a contaminated steak from a butcher in Spain.