04/26/2016 06:39 EDT | Updated 04/27/2017 01:12 EDT

Ukraine marks 30 years since 1986 Chornobyl nuclear disaster

KIEV, Ukraine — With flowers, candles and tears, Ukraine on Tuesday marked the 30th anniversary of the explosion at the Chornobyl nuclear plant, the world's worst nuclear disaster. Some survivors said the chaos of that time is etched in their minds forever.

A vigil was held at midnight Monday in the Ukrainian town of Slavutych, where many former Chornobyl workers were relocated, and more tributes were being held Tuesday.

About 600,000 people, often referred to as Chornobyl's "liquidators," were sent in to fight the fire at the nuclear plant and clean up the worst of its contamination. The initial explosion at the power plant killed at least 30 people, exposed millions to dangerous levels of radiation and forced a wide-scale, permanent evacuation of hundreds of towns and villages.

The final death toll from Chornobyl is subject to speculation, due to the long-term effects of radiation, but ranges from an estimate of 9,000 by the World Health Organization to a possible 90,000 by the environmental group Greenpeace.

Thirty years later, many could not hold back the tears as flowers and candles were brought to a memorial to the workers killed in the explosion. Some of the former liquidators who survived dressed in white robes and caps for the memorial, just like those they were wearing in the aftermath of the disaster.

Andriy Veprev, who had worked at the Chornobyl nuclear plant for 14 years before the explosion and helped to clean up the contamination, said memories of the mayhem in 1986 were still vivid.

"I'm proud of those guys who were with me and who are not with us now," he said.

Lidia Malysheva, a former Chornobyl worker whose family was relocated from Pripyat to Slavutych, said the memories of the disaster are embedded in all survivors' minds.

"We come here every year and every year it feels like the disaster was yesterday," she said. "People say 30 years has passed, but I can't believe that."

More commemorative events were being later Tuesday outside the Chornobyl power station as well as in Belarus and Russia, neighbouring countries that also suffered from the Chornobyl fallout.

Dmytro Vlasov, The Associated Press