Police investigating threats made against officers say a man arrested yesterday is no longer a suspect.

But the 31-year-old, who was arrested yesterday at a property in the West Midlands, is still being held by authorities.

Bosses at West Midlands Police called their officers and staff in to special briefings on Monday night and security measures were stepped up after the force received an anonymous telephone call.

Tuesday's arrest by counter-terrorism officers prompted reports of plans to kidnap and kill an officer, but police have now determined the threat was not terrorism-related.

Today police said: "A 31-year-old man arrested following threats to police officers and staff has been eliminated from police inquiries. However he remains in custody regarding immigration matters.

"Officers continue to investigate the circumstances behind the call to West Midlands Police but our assessment is that it was not terrorist-related nor is there any credible threat of a kidnap."

The briefings earlier this week advised officers not to go to work or go off shift in uniform, and also included a reminder about basic police station security measures.

The national security level remains at severe, meaning a terrorist attack is highly likely.

It comes after five men were charged in October with plotting to kill police officers or soldiers on the streets of London.