British police have arrested four more men in connection with a major terrorism operation linked to Pakistan.

The four men were arrested in their Birmingham homes Tuesday on suspicion of raising funds to finance terrorism and traveling to Pakistan to be trained as terrorists. The men are between 19 and 24 years of age.

Police say the arrests were pre-planned and were not in response to any immediate threat to public safety.

British authorities arrested eight people in September in connection with the ongoing investigation. Seven have been charged with terror-related offenses, including plotting suicide bomb attacks in Britain.