Jason Waite denied unlawfully killing his stepfather during a row in Snitterby, Lincolnshire.
The police's explosive disposal team has taken the substance away to be destroyed.
A man, 18, was arrested on suspicion of manufacturing a weapon and making an explosive substance.
A 100m cordon has been put in place in Waddingham while the substances are disposed of.
The A15 between Caenby Corner and Waddingham has now reopened.
