Officers investigated over Port Vale v Wolves trouble
Two officers are being investigated over their conduct during trouble between Port Vale and Wolverhampton Wanderers fans, Staffordshire Police have said.
More than 30 people were arrested after officers and a police car were attacked following the teams' game on 31 August.
A total of 22 people have been charged with a variety of offences.
A force spokesman said the officers were served with formal notices and wrongdoing should not be assumed.
He said the serving of notices was "routine in such circumstances".
Following the game, which Wolves won 3-1, trouble started near to Vale Park and around Burslem town centre in Stoke-on-Trent.
Officers were pelted with missiles and a police car was smashed up.
'Listen and learn'
The Independent Police Complaints Commission (IPCC) has said it received seven complaints relating to people being bitten by police dogs.
The trouble is also the subject of an independent investigation by Greater Manchester Police, which will publish its report at the end of the month.
The police spokesman said following a referral by the force, the IPCC directed it to conduct local investigations into dog bite complaints.
He said the watchdog also asked it to bring in public order experts from other forces to review and assess the policing operation and it "will again listen and learn from any recommendations made".
The force has also received "two further general complaints about the police operation, which are also being investigated," he said.
He added a debrief into the policing operation took place on 17 September and "debrief lessons have either been acted upon or are being progressed".