Michael Adebolajo claims he was injured in prison
Five prison officers have been suspended while police examine allegations of an assault on one of the two Woolwich murder suspects.
Michael Adebolajo, accused of killing Fusilier Lee Rigby in May, reportedly lost two front teeth in an incident at London's Belmarsh Prison on Wednesday.
The Prison Officers Association (POA) has denied any wrongdoing by officers.
It said a prisoner had been restrained by staff using approved techniques.
The organisation has criticised the Ministry of Justice for failing to take action to stop what it called "sensationalist reporting" of the incident.
A POA spokesman added: "Our members strenuously deny any wrongdoing and the POA will be supporting them legally and emotionally during this difficult time.
"The use of restraint is only used where necessary."
A prison service spokesman said that five members of staff had been suspended "while the police investigation is ongoing".