Chelsea are to write to fans – and warn them of potential bans – after a section of the club’s support launched into a sectarian chant at their 3-2 win at Fulham.During the west London derby a chorus of the ‘Flute for 50 pence song’ was clearly audible from the away section at Craven Cottage.The song includes the line ‘F*** the Pope and the IRA’ and its airing would appear to reflect the long-standing relationship between elements of the club’s support and that of Glasgow Rangers.Chelsea officials are aware of the chant, which is thought to have seen a resurgence in recent times, and have decided to act.Daily Mail Sport understands they will trace those who bought tickets for the fixture, and email them to ask them to avoid any repeat. It is likely to be made clear that anyone found doing so will face a ban from attending matches.The Football Association is thought to be aware of the situation. Chelsea have urged fans to stop chanting songs which say ‘f*** the Pope and the IRA’