Army bomb disposal experts were called after a suspected animal rights protest in which dozens of fireworks were thrown at a house linked to a guinea pig breeding centre.
The explosions in Burton-on-Trent were reported to police at 0245 GMT on Friday.
An army explosive team and police forensic experts were called to Portland Avenue, Branston and found fireworks had been thrown across the front gardens and driveways of two
homes in a row of three properties.
Around half of the devices had exploded and some had ended up underneath cars.
Staffordshire Police said no damage was caused and no one was injured, but part of the road remained sealed off as investigations continued into the attack.
A force spokesman said: "We are linking the incident to recent animal rights activity and an ongoing campaign of harassment focused on a guinea pig breeding centre in Newchurch, near Burton.
"One of the three properties involved has links to that business."
The incident is the latest in a three-year campaign against David Hall and Partners.
Last month leaflets were also dropped around the town of Chase Terrace, in Staffordshire, wrongly accusing a fuel supplier, and client of the firm, of being a convicted paedophile.