An oil depot near Kiev caught fire again on Saturday after firefighters had contained the massive five-day blaze that claimed the lives of five people. The authorities have launched a criminal investigation against the depot operator on ecocide charges.

A storage tank caught fire at the BRSM-Nafta facility in Vasilkov, 25 kilometers south of Kiev, at about 11:30am local time, the town’s mayor Sergey Sabov wrote on his Facebook page on Saturday.

The fire at the oil deport flared up again, after one of the tanks was depressurized resulting in a fuel leak, he added.

Sabov said there is risk of fire spreading to the adjacent storage tank. “There are four more full storage tanks with a 900-cubic-meter capacity,” he told reporters, adding that the risk of them catching fire is lower.

The State Emergency Service is monitoring the blaze said its head Nikolay Chechetkin. There are worries that there could be an explosion.

A video posted on Youtube on Saturday shows a billowing cloud of black smoke rising from the depot.

The firefighters “are not cooling the tanks due to very high temperature there and the risk of a repeated explosion,” he said. “As soon as it’s possible we will begin extinguishing the flames with foam.”

Posted by Сергей Сабов on Saturday, June 13, 2015

Posted by Сергей Сабов on Saturday, June 13, 2015

Firefighters have been battling the massive blaze at the oil depot since it started on Monday night. By Tuesday it had spread consuming more storage tanks and causing massive explosions, which killed five people and injured 18.

According to the state service, the fire was contained on Friday.

A video with dramatic bird’s-eye images shows the scale of the disaster. Much of the site is blackened and burned out.

The fire raised environmental concerns as a large amount of toxic substances were released into the air. On Friday the head of the investigative department of Ukraine’s Security Service Vasily Vovak said a criminal investigation has been launched against the depot’s operator BRSM-NAfta under the “ecocide” article.

Under article 411 of the Ukrainian Criminal Code, ‘ecocide’ - actions that may cause an environmental disaster – is punishable by imprisonment for a term of eight to fifteen years.

Locals told Ruptly video agency that there is a smell of smoke, but not as strong as it was earlier this week.

The wind is blowing the smoke from the depot fire towards Kiev, said Sabov as cited by UNN news agency on Saturday.

“The smoke contains plenty of hazardous substances including benzopyrene, which is very a harmful carcinogenic, the first class of danger,” head of Kiev’s Ecological-Cultural Center (KECC) Vladimir Boreyko told UNN warning the capital’s residents to stay home.

Experts believe the disaster could have consequences not only for the Ukrainian capital, which has a population of around three million people, but also for neighboring European countries.

READ MORE: Drone footage of Ukrainian oil depot blaze shows scale of disaster (VIDEO)

“Whenever you have hydrocarbons like this burning, releasing all sorts of carcinogenic substances, and the smoke particles themselves are toxic, there is the danger of exposure to what are potentially carcinogenic materials,” Tim Mousseau, a biological sciences professor at the University of South Carolina, told RT. “Certainly, there is a potential hazard to anyone who is engulfed by the smoke.”

Chechetkin said on Saturday that local health authorities are monitoring the level of harmful substances in the air which “do not exceed the maximum admissible concentration.”

The Interior Ministry also has an ongoing investigation into the causes of the fire. Zoryan Shkiryak, an aide to Interior Minister Arsen Avakov, said on Tuesday that the cause of the blaze could be arson or a violation of safety regulations at the facility.

Investigators said that the BRSM-Nafta company’s oil depot could have been set on fire by its owners to destroy oil products involved in a criminal case, Ukrainian National Security and Defense Council Secretary Alexander Turchinov said Thursday.

On Friday , the oil depot administration announced a million hryvnia (nearly $50,000) award for accurate information about the perpetrators.