Chelsea's impending transfer ban for breaking rules about signing foreign under-18 players appears to have opened a can of worms.

A statement from FIFA on Friday confirmed the Blues have been fined £460,000 and will be unable to sign new players in the next two transfer windows.

Chelsea were found to have breached regulations in 29 out of 92 cases investigated. They've since appealed the ban and could have it suspended for 2020.

It's now being reported that Manchester City are also subject to an investigation and could be punished in the same way Chelsea have been.

According to the Daily Mail, City have been accused of playing two African players, named George Davies and Dominic Oduro, as trainees before they turned 18.

FIFA have rules in place preventing clubs from taking young footballers from their home countries, so City could be in trouble.

And it gets worse. A new report from German magazine Der Spiegel, per the BBC, claims City's signing of Jadon Sancho in March 2015 may have been illegal.

When the England winger was 14 years old, City made a banned payment of £200,000 to his agent, Emeka Obasi, and listed it as an "agent fee" in the documentation.

But FIFA rules say players under the age of 16 cannot be represented by an agent. City's payment was said to be as part of a "scouting contract" for central and South America at the time.

Der Spiegel's report adds that the Citizens wrote a letter to Sancho's father detailing how much they were prepared to pay the youngster once he turned professional.

Due to the fact rules also state clubs can't offer financial inducements to players under 16, a lawyer working for City at the time was "alarmed" that their letter may have been illegal.

City have released a statement saying: "The attempt to damage our reputation is organised and clear.

"We will not be providing any comment on out-of-context materials purported to have been hacked or stolen from City Football Group and Manchester City personnel and associated people."