A second suspect has been arrested after boxes of live mice were released into McDonald's restaurants in Birmingham.
A 30-year-old man is now in custody over the apparent protests, West Midlands Police said.
Videos on social media show the rodents being released in branches in Star City, Perry Barr and Small Heath.
A 32-year-old man, previously arrested in connection with the incidents, has been released on bail.
A video on social media showed mice dyed in the colours of the Palestinian flag being released into the Star City restaurant on Monday.
A second clip also showed mice in a box in the Perry Barr branch on Tuesday.
The force said: "Our position is clear, this is appalling, and will not be tolerated."
Patrols across the region have been increased to reassure communities, police added.
Both restaurants were temporarily closed for a full clean and visits from pest control officers, a McDonald's spokesperson said.
A video of a reported third incident of a similar nature was also shared on social media on Wednesday, where a group of masked people appeared to empty a box of mice in a branch in Small Heath.
West Midlands Police said it was investigating the third incident but it was unclear if it was connected.