A girl has been taken to hospital with a head injury after a collision with a scrambler bike.
The emergency services were called to a report of an incident on Ashtons Green Drive in St Helens at 2.50pm today.
The 15-year-old girl was taken to hospital for treatment to a head injury, which was not thought to be life-threatening.
Two boys, aged 12 and 16, both from St Helens, were arrested shortly afterwards in the Watery Lane area on suspicion of theft of a motor vehicle and motoring offences.
The scrambler bike has been recovered from the scene and will be forensically examined.
Chief Insp Tony Jones said: "Our inquiries into this incident are at an early stage but we believe the scrambler bike was being ridden in a dangerous and anti-social way prior to the collision and mounted the pavement. It is not believed the males were wearing helmets.
"The riding of scrambler bikes in this way is putting other road users and pedestrians at risk. These people have no regard for anyone but themselves and don’t care about the risk they pose to others.
"If you saw this bike being ridden by two males in anti-social manner at around 2.30pm please come forward.”
He added: "We will continue to take pro-active action against those involved in the criminal use of scrambler bikes on our roads and will do everything possible to locate and seize suspected stolen or nuisance bikes and arrest those who are putting the safety of others at risk.
"I would like to take this opportunity to reassure communities across Merseyside that we understand their concerns about scrambler bikes and are relentless in our efforts to tackle them.
"Such behaviour cannot and will not be tolerated on the streets of Merseyside and our response reflects how seriously we take this issue.
"I would urge anyone with information which could help us take these bikes out of circulation and make our streets safer to keep coming forward."
Anyone with information on who is using these bikes and where they are being stored is asked to call police on 101 or Crimestoppers, anonymously, on 0800 555 111.