Compounding the catastrophe was the lack of transparency from the Soviet Union. In the days that followed, Soviet officials refused to elaborate on the extent of the disaster. The accident occurred on a Friday night, when the reactor's cooling system failed during a test. Then followed the nuclear meltdown on Saturday, which caused the explosion and the radioactive discharge.
When Sweden initially contacted the Soviet Atomic Power Inspection Board, Moscow denied that an accident had occurred. However, as Sweden, Denmark, Finland and Norway reported unusually high levels of radioactivity, Moscow was forced to officially announce the accident.
The public outcry for more information forced the normally tight-lipped Soviet government to make an acknowledgement, and that in itself was no ordinary event.
But the first Russian televised announcement a day after the accident was brief. It showed a black-and-white photo of the Chernobyl plant supposedly taken by a worker after the accident. The TV commentator then told viewers that Western reports of fires and extensive damage were unfounded, and that cleanup efforts were steadily moving forward.
"The trouble has passed," he said.
Yet safety experts remained unconvinced. Even more worrisome was the struggle to control a graphite fire, which was releasing radioactive material into the air.
While the Soviet government was busy reassuring countries that there was no danger, scientists from around the world began piecing together information based on accounts from Sweden, which was 700 miles from Chernobyl. As one U.S. nuclear scientist put it at the time, "If the radioactivity is a few millirem 700 miles away, I'd hate to be within 10 miles."
Still, the Soviets refused to give more details. In the United States, a Soviet Embassy official proclaimed: "The problem is getting better. It is not out of hand. It is improving. But unfortunately, it is not over yet."
Information inside Russia was sparse, too. Russian residents and even some officials were left unaware that the accident had occurred. In the news reports that trickled out, Soviet media stated that nuclear accidents like Chernobyl were "virtually impossible."
U.S. officials were equally frustrated at the Kremlin's silence. President Ronald Reagan initially told reporters that he wasn't annoyed by Moscow's handling of the crisis. But privately, he was highly critical. Speaking at a summit in Indonensia, he said "the Soviets owe the world an explanation."
"The Soviets' handling of this incident manifests a disregard for the legitimate concerns of people everywhere," Reagan said. "A nuclear accident that results in contaminating a number of countries with radioactive material is not simply an internal matter."
It took a week for a full account to come out.
Pravda, the official Communist Party daily, eventually confirmed suspicions by experts around the world: that a fire and explosion spewed radioactive materials into the air. Yet it still said the situation was "under control."
The paper also mentioned the four-hour evacuation that took place in Pripyat -- the town specifically built to house residents working at the Chernobyl plant -- and described how the firefighters "kept fighting the blaze courageously." It also thanked those who helped evacuate the town "although it was a Saturday."
Of course, first-hand accounts years later paint a much different scene. Yuri Andreyev, speaking to the AP, described the chaos that took place at the plant -- how water that was used to cool down the reactor simply evaporated and how the firemen sunk in the melted asphalt.
In the town itself, pandemonium ensued as residents packed into boats on the Pripyat River to escape.
The Soviet Union's refusal to release any information speaks to the mentality of the Kremlin. Perhaps the best explanation of trying to make sense of this mentality came from Ellen Goodman writing in 1988, shortly after the accident:
Exactly a year ago, in Moscow, I had a conversation with a young journalist who acted as interpreter. After a session with three bureaucrats, which bored him as much me, we went to a local coffee shop and talked about journalism and censorship.
Andre was among the elite of his Soviet generation. He was informed about America -- down to our frequent-flyer coupons -- and not reflexively defensive about the Soviet system. Yet, at one point, animatedly debating our countries' attitudes toward information, he reached for this analogy, "In the U.S.S.R. we do not tell a patient if he has cancer. Many times we treat people like they are children to be protected."
And in many ways, those living in the Soviet Union at the time would have agreed.
See past coverage of Chernobyl: