All three London Bridge attackers wore the belts
British police say the use of fake explosive belts, as worn by the London Bridge attackers, is a 'new tactic'.
They have released images of the leather belts, which were strapped with disposable plastic water bottles wrapped in silver masking tape.
All three of the attackers wore the belts, which were still attached to them when they were shot dead.
UK police Commander Dean Haydon, who is leading the investigation, said: "I have not seen this tactic in the UK before where terrorists create maximum fear by strapping fake explosives to themselves.
"Anyone who saw them on the night would have thought they were genuine.
"It is hard to speculate what the motive was for wearing the belts.
"It could be that they had plans to take the attack in to a siege situation or it might be that they saw it as protection from being shot themselves.
"It makes the bravery of those police officers and members of the public who tackled the terrorists even more remarkable.
"The belt would have been visible to them and if you are fighting back or aiming a shot at someone wearing the device you would clearly be very aware that you could be caught in an explosion."
Officers have so far spoken to 262 people from 19 different countries in relation the June 3rd attacks that killed eight people.
Of these, 78 are classed as 'significant witnesses'.
Police believe there are many others who witnessed the incidents who have yet to come forward.
They have also made a special appeal to Irish people who may have information relevant to the investigation.