The FA has already started inquiring into the pitch invasion at Cardiff last weekend, as well as the missiles thrown at players at Stamford Bridge in midweek.

Now they are ready to take further action after a meat pie and two plastic bottles were hurled at assistant referee Phil Barston by Millwall fans during the First Division game against Birmingham on Thursday.

An FA spokesman confirmed that the governing body are still "awaiting the reports from the match officials" before deciding upon their course of action.

However, there is little doubt that the incidents at Millwall will be added to an ever-growing list of investigations, while both managers could yet face disciplinary action from the FA as well.

Millwall boss Mark McGhee was banished from the touchline for verbally abusing fourth official Bill Jordan, while City boss Steve Bruce was also sent to the stands after protesting at the dismissal of Curtis Woodhouse.

McGhee apologised for having "lost the plot" and vowed that the club would root out those responsible.

"It's concerning to us all and I can say on behalf of the chairman that he will do everything he can to find out who is responsible and they won't be welcomed back here," he said.

"We are totally committed to try and eradicate it."

And Millwall chairman Theo Paphitis said he would "ban for life" the troublemakers responsible for throwing missiles.

Paphitis made it clear that such scenes would never again take place at The New Den while he was chairman.

"Those responsible will be prosecuted and banned for life," he told BBC Radio Five Live.

"We won't tolerate anything like that and we're not prepared to let anything get out of hand.

"The problem is that fans see this sort of behaviour on television and you get copycats.

"We've got to stamp on this and stamp on it hard because it might be a meat pie today, but who knows the next time.

"We won't tolerate anyone going onto the pitch.

"My concern recently has been that with people going onto the pitch, not enough has been done to make it clear that this is unacceptable.

"It cannot be tolerated."