On Tuesday, West Midlands Police said counter-terrorism officers had received a tip-off that staff were in danger and were taking it "extremely seriously".
A 31-year-old man arrested in connection with the call has since been eliminated from inquiries.
The force said its assessment was that the call "was not terrorist-related or a credible kidnap threat".
Inquiries into the original call are continuing and West Midlands Police said the man would remain in custody in connection with "immigration matters".
The force had previously urged officers to take extra precautions, including not wearing uniform on the way to or from work.
Staff were first told of the threats on Monday night.
The national security level remains at severe, signifying a terrorist attack is highly likely.
In October the threat level to police officers across the country was raised to "substantial".
A threat to kidnap and murder a serving police officer was "not credible", a force has said.