(LONDON) -- Britain's Home Office announced that the Joint Terrorism Analysis Centre (JTAC) reduced the international terror level from "severe" to "substantial" on Monday.
"The change in the threat level to substantial does not mean the overall threat has gone away -- there remains a real and serious threat against the United Kingdom and I would ask the public to remain vigilant," said Home Secretary Theresa May.
"Substantial" means there is a strong possibility of an attack. Since the threat system was first used in 2006, the highest level of "critical" -- meaning an attack is imminent -- was reached twice: in August 2006 and June 2007.
The JTAC, which was established in 2003, collaborates with law enforcement agencies to assess intelligence relating to international terrorism.
Copyright 2011 ABC News Radio