This map shows the locations across the South East where suspect packages have been found in the last three days.
The blue markers designate packages that were found on Tuesday, green is for yesterday and the red markers are for today.
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The letter was signed by the CBI, British Chambers of Commerce, the EEF, the Institute of Directors and the Federation of Small Businesses.
A spokesperson said Rory Stewart's remarks were in line with the British government’s stated position.
The minister's intervention will come a week after Trump decertified the landmark agreement claiming it was not in the US national interest.