The 15-year-old, who stands at 6ft 2in, has been the standout performer in a holding midfield role as Gambia's Under-17s, known as the Baby Scorpions, reached the final of the WAFU Zone A tournament in Senegal, beating the hosts 5-3 on penalties in Monday's final in Dakar.
Jeng, who turns 16 in December, has come through the Samger FC academy, a system that has previously produced Sulayman Marreh, who went on to play for Watford, and Musa Ann, who has attracted interest from Manchester United.
Bayern Munich, Benfica, Sporting CP and Paris FC were all watching Jeng in Dakar alongside Chelsea, and are expected to continue tracking him as they weigh up a move.
Chelsea are said to see him as a potential star in the making and are assessing whether to move quickly to get ahead of their rivals, with Monaco and Union Saint-Gilloise also reported to be in the running.
The interest reflects Chelsea's approach to recruitment at the youngest age groups, where the club has been highly active in identifying prospects before they attract wider attention. No formal offer for Jeng has been reported at this stage, and any transfer would in any case be some way off given his age and FIFA's rules on international moves involving minors.
Jeng impressed scouts throughout the tournament with his composure on the ball and his range of passing from deep midfield, qualities that stood out even as Gambia needed penalties to see off the host nation in the final.
His performances have made him one of the most talked-about names to emerge from West African youth football this year, and the level of interest already shown suggests his next move, whenever it comes, will be closely watched.