The FBI searched a Jersey City home Wednesday while investigating a series of threatening letters.

Authorities say that the letters contained threats, some of which targeted Rockefeller Plaza in New York City.

Investigators were seen removing computers and other materials from the Oakland Avenue home.

Officials tell News 12 New Jersey that they believe they know who wrote the letters, but no arrests have been made.

Sources tell News 12 that there is no active threat or plot and that the letters are not linked to any Islamic State groups.