Fox News reporter Chad Pergram has tweeted that the letter sent to Barack Obama and the letter sent to Senator Roger Wicker yesterday - which tested positive for the poison ricin - contained 'similar language' and were 'signed identically'.
Letters sent to Obama & Wicker contain similar language and are signed identically.
More top news
A man with no recollection of who he is has been found in London, with police appealing for help to identify him.
Taxi booking service Uber has reportedly been valued at nearly $51 billion.
Two people have been charged with manslaughter after a woman died while bungee jumping in Spain.