CONCRETE SUPPLIER RMC was last week the target of a terrorist attack by animal rights activists protesting against its involvement in the construction of an animal research centre at Oxford University.
The company received a 'suspect letter' two days after a 'trashing raid' on its Rageley quarry in Warwickshire which caused extensive damage.
Anonymous posters on the Arkangel animal rights website claimed responsibility.
'It turned out not to be a letter bomb but one of the tricks of these people is to cause real concern to people, ' said a RMC spokesman. He would not elaborate further.
The motive for the attacks is cited as the supply by RMC of concrete to the £16M centre.
Protesters have targeted the scheme's contractor Walter Lilly, as well as suppliers.
RMC said it was reluctant to comment. 'We cannot give weekly press reports - that is in fact the aim of these groups.'
The company said its contract runs from the beginning of March this year until the end of the summer.
The new centre consolidates existing research facilities according to Oxford University.
A university spokeswoman said that the centre was not for 'primate research' and that 98% of the animals used were rodents.