Greater Manchester Police Assistant Chief Constable Garry Shewan has revealed details of an arrest made over an offensive Facebook page created after the deaths of PC Fiona Bone and PC Nicola Hughes.
Speaking at news conference, he said an investigation by Greater Manchester Police and Merseyside Police led to the arrest of a 22-year-old man from Merseyside last night.
He remains in custody and is being questioned.
More top news
One of four men accused of plotting to use a moped in a series of drive-by shootings in London has changed his plea at the Old Bailey.
The North Yorkshire town was divided since the historic bridge was damaged by floods at Christmas.
Syrian President Bashar al-Assad has vowed to regain control of the entire country but warned it could "take a long time".