A fourth independent inquiry has been launched into claims of police brutality during the G20 protests.
Officials at the Independent Police Complaints Commission (IPCC) said a woman has claimed she was assaulted while held in a "kettle".
The alleged incident took place when police contained a group in an alleyway connecting Bishopsgate and Great St Helen's on 1 April.
The probe is one of four ongoing investigations into claims of police violence during demonstrations in the City of London.
Officials are also investigating the circumstances of the death of newspaper seller Ian Tomlinson, 47, after he was apparently hit with a baton and pushed to the ground.
Two other probes centre on an incident in which protester Nicola Fisher was slapped across the face and the alleged assault of a 22-year-old woman at an impromptu climate camp.
Meanwhile, 131 complaints have been forwarded to the Metropolitan Police to see if officers can be identified and linked to allegations.
So far, officials are examining 52 of these cases where an officer was identified in connection with a complaint in which someone was injured.
Of these, 44 are being investigated by whatever force the officer worked for, under the supervision of the IPCC.
Officers from the Met, City of London Police and British Transport Police (BTP) were involved in the two-day public order operation.
The 131 complaints were some of 276 complaints made to the IPCC.
Some of them have been discounted because they were made by people who saw the demonstrations on television.
An IPCC spokeswoman said 78 complaints relate to police tactics and have been passed to HM Inspectorate of Constabulary.
Officials at the Government department, led by Denis O'Connor, were conducting a review of the tactics used during the G20 demonstrations.
Officials are also investigating whether a statement made by the Metropolitan Police in the wake of Mr Tomlinson's death was misleading.
A sixth IPCC investigation into alleged excessive force by an officer against a 23-year-old man at the climate camp was dropped after he withdrew his complaint.
But a supervised internal inquiry will continue into claims an officer used the edge of his shield to assault the man as the camp was cleared.
A series of angry clashes during the G20 protests were broadcast around the world and provoked a storm of controversy about police tactics.
Senior officers have come under fire over the practice of "kettling" demonstrators by holding them in one place for lengthy periods of time.
Many clashes between police lines and surging groups of demonstrators were captured by amateur cameramen using mobile phones.