West Ham United and Millwall face the prospect of severe punishment after being hit with several Football Association charges following the crowd trouble which marred their Carling Cup match last month.
The FA have issued four charges against the Hammers and three against Millwall - including indictments for racist behaviour by both sets of fans - following the shocking crowd violence in and around Upton Park on August 25.
A full range of sanctions are available to the FA, including the clubs being made to play matches behind closed doors and fans being banned from attending football matches for life.
An FA statement said each club faces charges of:
• Failure to ensure their supporters refrained from violent, threatening, obscene and provocative behaviour.
• Failure to ensure their supporters refrained from racist behaviour.
• Failure to ensure their supporters did not throw missiles, harmful or dangerous objects onto the pitch.
West Ham have also been charged with failure to ensure their supporters did not enter the field of play - there were three pitch invasions during the second round cup tie.
Hammers striker Carlton Cole and Millwall's Jason Price both suffered racist abuse and during the course of the evening, one 44-year-old man was taken to hospital with stab wounds and several others were injured.
The chaotic scenes at Upton Park also resulted in a total of 200 seats and a toilet block in the visiting supporters' section of the ground being damaged.
The FA's statement added: "The FA has liaised closely with all relevant authorities including the Metropolitan Police during the course of its investigations and has been in constant dialogue with both clubs during this time.
"Both clubs now have a period of 14 days to respond to the charges."
West Ham reacted to the charges by defending their preparations for the game and reiterated that they will take their own action against any fans found responsible of unacceptable behaviour.
A Hammers spokesman said: "We are reviewing the FA charges and will respond accordingly. In advance of the Millwall match, the club followed the strict advice of the police and relevant authorities at every stage of the planning process.
"That full cooperation continued on the night with the club working closely with police on a carefully set-out plan that was initiated and approved by the independent safety advisory group.
"We do acknowledge the appalling behaviour of a minority of fans inside the stadium and, in conjunction with the police, will continue to take strong and appropriate action against anyone found responsible."
Millwall responded by saying they were "shocked and disappointed" by the charges. The League One side said some fans had won some praise for their behaviour and the club were powerless to influence actions in another club's stadium.
The club said in a statement: "Millwall Football Club are shocked and disappointed that charges have been profferred against us in respect of events that took place at West Ham United on Tuesday 25th August 2009.
"We maintain that we did everything in our power with regard to our ticketing arrangements for this game. Furthermore we expressed our concerns in advance about ticket allocations and arrangements in general.
"It was widely acknowledged that none of our supporters came onto the pitch, and indeed the behaviour and forbearance of our fans brought praise from media observers on the night.
"Our question for the Football Association is what can Millwall Football Club do to control individuals' actions once inside our opponents' stadium. We have, and we continue to assist the authorities in their investigations into the events of that evening."