A regional outpost of Russia’s Kommersant business newspaper received a written death threat in an attack on its Yekaterinburg office over the weekend, police said.

The motive behind the break-in was not immediately clear, Sergei Plakhotin, general director of the Kommersant-Ural publishing house, told the local e1.ru news website. The outlet speculated that the attack may be linked to the publishing house’s publication last fall of a book about the local criminal underworld in the 1990s.