Russian Telegram channels 112 and Baza reported the information.
According to Baza, the drone fell near the hydrocracking unit at the plant. It happened around 7 am Moscow time.
The crash site has been cordoned off, and a demining team has been called to the plant.
According to preliminary data from the Russian media, there were no casualties as a result of the attack.
Later, the governor of the Yaroslavl region, Mikhail Evraev, said that the electronic warfare system of the Slavneft-Yanos oil refinery had allegedly prevented the drone attack.
"Law enforcement agencies and special services are working at the scene. No injuries, no fire," he wrote.
For reference: According to the official website of the company, Slavneft-Yanos is one of the ten largest oil companies in Russia in terms of oil production.
The night before, Russian occupying troops launched 8 attack drones and a ballistic missile at Ukraine. Ukraine’s air defense forces managed to destroy all the drones.