An 11-year-old child was taken to hospital with serious injuries, although these are thankfully not life-threatening.
Police and North West Ambulance Service attended, and a scene was established, but has now been closed.
The 35-year-old woman was arrested on suspicion of having a dog dangerously out of control.
She remains in police custody for questioning.
Superintendent Nicola Williams, of GMP City of Manchester Division, said: “This is an awful attack that has left an 11-year-old boy with serious injuries and his family are understandably incredibly distressed by what has happened.
“I understand the concern an incident of this nature will cause in the wider community, and I want to reassure you that we will carry out an extensive investigation into what has happened.
“The dog has been secured and we have made an arrest of a woman who remains in police custody.
"Our investigation is in its early stages, but we are seeking to understand the full circumstances and will take appropriate action.
“We are appealing to anyone with information, who witnessed this incident, or has footage - including CCTV, mobile or dashcam - to make themselves known."
You can make a report by calling 0161 856 1146 quoting log 1530 of 4 June 2023, or you can use the LiveChat function on GMP’s website: www.gmp.police.uk
Alternatively call the independent charity Crimestoppers anonymously on 0800 555 111.
