Doctors for Bolton Wanderers midfielder Fabrice Muamba say they cannot explain the reasons behind his cardiac arrest.

Despite a battery of tests, world-renowned experts still have no idea exactly why he crashed to the turf during the abandoned FA Cup tie at Spurs last month and "died" for 78 minutes.

A source close to him told The Sun: "It's hard to believe but Fabrice is kicking a ball again.

"It was just a game of keepy-uppy but no one would have thought it possible a few weeks ago.

"He's had all sorts of tests but none of the specialists are sure why he collapsed. All they know is that he has had one of the most amazing recoveries in medical history."