Russia's 2014 World Cup squad were subject to extra doping tests, former FIFA chief medical officer Jiri Dvorak told BBC Sport.

Dvorak said the tests adhered to correct procedures and were carried out because of rumours about Russian athletes, but they came back negative.

"We heard some rumours about xenon in Russia, so we decided to test that," Dvorak said.

"We just tested the Russian team for that because the substance was unknown in the rest of the world. All tests were negative."

Xenon, a gas used to encourage the growth of red blood cells that increase stamina, was used at the 2014 Winter Olympics in Sochi by some Russian athletes.

Allegations of a state sponsored doping programme that benefitted Russian footballers is being investigated by FIFA president Gianni Infantino.

Infantino said that the Russia squads that competed in the 2014 World Cup and 2016 European Championship were tested thoroughly and came back clean.

He said: "These tests are not done in Russia. It's all done outside Russia in Wada-accredited laboratories and they have given negative results.

"These are the facts that need to be remembered. We have all seen the different reports, we are collecting information and if there have been any anti-doping violations, measures will be taken. We always have a zero-tolerance policy for doping."