This article originally appeared at Radio Free Europe

Russian officials say the raid they have conducted on a chocolate factory owned by Ukrainian President Petro Poroshenko was seeking evidence for a tax-fraud case.

Russian news agencies said masked riot police surrounded a Roshen factory in the western city of Lipetsk on April 1 and blocked the entrance.

Vladimir Markin, spokesman for Russia's Investigative Committee, said the detectives were searching for material related to a suspected fraudulent tax rebate of more than 180 million rubles (some $3.1 million) received by Roshen.

Roshen released a statement that said the chocolate maker considers the "tax check to be unacceptable and illegal."

Ties between Moscow and Kyiv are severely strained over Russia's takeover of Crimea and Kremlin support for rebels fighting government forces in eastern Ukraine.

Poroshenko accused Russian authorities last month of interfering in plans to sell the Lipetsk factory.

Roshen laid off some 400 of its workers in November, saying it was reducing operations.