What to Know Investigators launched the search over threatening letters, including one that claimed there could be an attack on Rockefeller Center

Other threatening notes were also sent to several NJ locations, officials said

Investigators said no arrest was made, but they believe they know who wrote the letters.

FBI agents and local police searched a home in Jersey City Wednesday in an investigation into numerous threatening letters, including one claiming there might be an attack on Rockefeller Plaza, law enforcement sources said.

Other threatening notes were also sent to several NJ locations, officials said.

Investigators said no arrest was made, but they believe they know who wrote the letters. Agents and police seized computers and other materials from the home along Oakland Avenue during a search that lasted several hours.

Investigators said there was no active threat or plot. The investigation into the writings is not believed to be linked to any terror- or ISIS-inspired postings.

Rather, the person who wrote the letters may be angry or emotionally disturbed, two sources familiar with the case said.

An FBI spokeswoman declined to comment except to confirm agents were on "official business" at the Oakland Avenue home.

A spokesman for the US attorney referred calls to the FBI.