The Russian troops occupying Chernobyl will soon suffer the effects of the radiation exposure after digging trenches in the nuclear zone, the head of Ukraine’s state service for the management of the Exclusion Zone said on Wednesday. Yevhen Kramarenko told reporters that Russian troops, who had occupied the Chernobyl blockade for five weeks, had dug trenches and shelters for their vehicles in an area known as the Red Forest. The Red Forest is a 1.5-square-mile pine forest that died as a result of radiation exposure shortly after the Chernobyl nuclear accident in 1986. It remains the most polluted part of the exclusion zone, according to Reuters. “We believe very soon [the Russians] they will feel the effects of the radiation they have received. “Some of them will feel it in months, some in years,” Kramarenko told a news conference Wednesday. “But anyway, all the soldiers who were there will feel it at some point.” He also confirmed previous reports of Russian soldiers driving around the Red Forest without any protective equipment and inhaling clouds of radioactive dust. Radiation poisoning can cause different effects depending on the strength and duration of exposure, according to the Centers for Disease Control and Prevention (CDC). In more extreme cases, radiation poisoning can lead to internal bleeding and skin burns, as well as thyroid cancer and cardiovascular disease, according to the CDC. Russian troops left the buffer zone earlier this month after some of their soldiers “panicked” at the first signs of radiation sickness, Ukraine’s state-owned energy company Energoatom said, according to The Guardian. It is not clear exactly what their supposed symptoms were, although they “appeared very quickly,” Energoatom added. Russian troops have since gone to Belarus and Russia, Kramarenko said, adding that Ukrainian plant officials were now working to develop additional security measures to “avoid any future incidents.” The power plant was completely decommissioned after the 1986 nuclear accident and the rest of the work at the construction site is mainly focused on decontamination. Kramarenko said it was unclear how high levels of radioactivity were around the site at the moment, as there was no electricity at the moment. “Until then we will not understand the damage done,” he said.