Police are seeking three men suspected of releasing cockroaches inside two branches of Byron Hamburgers following revelations that the restaurant chain aided a Home Office immigration sting.

Officers from the Metropolitan police public order unit have released images of the men they want to speak to in connection with the incidents on 29 July at Byron restaurants in St Giles High Street and Holborn in central London.

In the first incident cockroaches and locusts were released on the restaurant floor and in the men’s toilets. “The suspects then moved on to a second branch of the chain in High Holborn where they also released insects,” the Met said.

On both occasions, customers were asked by staff to vacate the premises and the restaurants were closed.

The protest was organised by a group calling itself London Black Revolutionaries, following reports that 35 kitchen workers from Brazil, Nepal, Albania and Egypt were arrested after being duped into attending a meeting about the dangers of cooking burgers rare or medium rare.

Byron restaurant in Holborn, one of two branches where the insects were released. Photograph: Amer Ghazzal/Rex/Shutterstock

The meetings in 12 London branches of the burger chain were in fact a joint operation with immigration enforcement officers who came to the restaurants with names and photographs of foreign workers supplied by management.

The police described one of the suspects, Man A, as “dark-skinned, of medium to heavy build, unshaven with thinning hair”. They said he was wearing a bulky hooded anorak, brown shoes and blue jeans and was carrying a rucksack.

Man B was described as “dark-skinned, of thin build, with long hair – tied at the back – and unshaven. He wore thick-rimmed glasses and a black tracksuit with white stripes along the arms, and carried a bag or satchel over his shoulder.”

The third suspect was dark-skinned, of thin build with short hair and a short beard. “He was wearing a brown blazer, blue shirt and light grey or beige trousers,” police said.

The Home Office confirmed that 25 of the 35 workers arrested during the operation at Byron have been removed from the UK, with others still going through the removals process.