A terror threat to the Belgian capital has decreased slightly but heightened security measures are being maintained for the time being, officials said Thursday, according to AP. Authorities have warned of an increased risk of attack after police on Dec. 21 detained 14 people suspected of plotting to help an accused al-Qaida militant break out of jail. Based on partial results of an inquiry into the suspected plot and intelligence information gathered nationally and abroad, the terror alert to Brussels has dropped from Level 4 _ the highest _ to Level 3, said Alain Lefevre, a director at the government Crisis Center. «However, that does not mean we can let our guard down. A certain number of security measures _ both visible and less visible _ remain in place,» Lefevre said. The al-Qaida-linked inmate, Nizar Trabelsi, is a Tunisian former professional soccer player who is serving 10 years for plotting to drive a car bomb into the cafeteria of a Belgian air force base housing about 100 U.S. military personnel. The police are continuing an investigation into material found in the raids on the suspects' homes, Lefevre said without elaborating. All 14 have been released for lack of evidence, and all have maintained their innocence. Trabelsi himself has denied that his supporters were plotting his jailbreak or any terror attack.