More time is needed to decide if anyone connected to West Midlands Police will face charges over the Hillsborough disaster, prosecutors have said.
The force carried out the first investigation into South Yorkshire officers' conduct during the 1989 tragedy.
It has been claimed both colluded in a "cover-up" to pin the blame on fans.
The Crown Prosecution Service has requested more time to investigate.
However, it said it was still on track to announce whether there will be criminal charges relating to South Yorkshire Police by the end of June.
The Independent Police Complaints Commission handed its files to the CPS in January.
It is still investigating more than 170 allegations of police misconduct.
The IPCC said Durham Constabulary will examine files relating to a retired South Yorkshire Police officer after any charging decisions have been made.
A jury concluded in April last year the 96 victims of the tragedy were unlawfully killed.
They found fans were fatally crushed at the FA Cup semi-final between Liverpool and Nottingham Forest amid a "dangerous situation" created by police errors.