Radioactive traces on BA planes

BBC reports that radioactive traces have been found on three Boeing 767 airliners operated by British Airways. Two of them have been grounded at Heathrow airport while the third is on the ground at Moscow’s Domodedovo airport awaiting an inspection by British forensic investigators. Apparently, BA is trying to make contact with the 330,000 passengers who traveled on the planes affected since the suspected contamination. The traces could have been left by someone who was in contact with poisoned Alexander Litvinenko or by someone who has brought the substance to the UK.