
Police said the UK Ijtima event at Shrubland Hall was forced to end early after officers identified a "potential serious threat" to the gathering.
The UK Ijtima is organised by the Tablighi Jamaat movement and is considered one of the largest annual gatherings of Muslims in the UK, drawing worshippers from across Britain and abroad.
Organisers of the event, which ran from 9 to 13 July, were told to close it early as a precaution to allow the 15,000 people in attendance to leave safely.
CTP did not give further details on the nature of the alleged plot but described it as a "serious" threat.