On this day in 1986, the reactor explosion at the Chernobyl Nuclear Power Plant sent radioactive fallout across Europe.
The explosion killed 31 people, and millions were exposed to dangerous radiation levels. The U.N. estimates upwards of 4,000 deaths have been linked to radiation poisoning from the event.
Reactor No. 4 at the power plant 65 miles north of the capital Kyiv exploded and caught fire deep in the night on April 26, 1986, shattering the building and spewing radioactive material high into the sky.
The catastrophe was worsened by reluctance from authorities to inform the public. About 2 million residents of Kyiv weren't informed of the fallout danger. News of the disaster only became known worldwide after rising radiation levels were detected in Sweden.
Eventually, more than 100,000 people were evacuated from the vicinity and a 1,000-square-mile exclusion zone was established where the only activity was workers disposing of waste and tending to a hastily built sarcophagus covering the reactor.
The Associated Press contributed to this report.