More than 30 officers from Wiltshire and Dorset police executed a search warrant at the premises of Dorset-based transport and logistics firm Taymix last month following a fatal accident on the A303.
Two people died in the accident, at West Knoyle, Wilts, at 3.30pm on 2 March. The vehicle they were travelling in was hit by a Taymix-owned ERF artic and pushed onto the opposite carriageway, where it was struck by another car.
The Polish driver of the Taymix tanker was arrested and bailed by the Chippenham magistrates until 14 April.
Police officers raided the joint premises of Taymix and Translact Ltd in Pimperne, Dorset, together with a number of private addresses, as part of their investigation into the accident.
A spokesman for Wiltshire Police said: "We will now be undertaking extensive analysis of the items recovered. It is anticipated that it will be some time before we have a clear picture of the circumstances leading to the collision."
Taymix declined to comment.