The FBI is actively scrubbing its intelligence databases in order to identify any possible US-based connections to the New Zealand shooter, according to a law enforcement official who was speaking on background.

FBI headquarters is requesting all field offices review their case files and threat management systems for any subjects who may have expressed an interest in attacking religious institutions or may otherwise be motivated to conduct a retaliatory attack, the source said.

FBI management has tasked its field offices with proactively contacting informants who may be in a position to report on related threats to the homeland.

The FBI is closely monitoring the situation in Christchurch and is engaged with its law enforcement partners in New Zealand, according to the source.