An expert commission, which is currently investigating the ammonia explosion at a plant of the Stirol Concern in Horlivka, Donetsk region, currently has three theories about what happened: a violation of equipment operation procedure, negligence by maintenance staff, or the violation of safety rules.

A team of investigators of the General Prosecutor's Office has arrived in Horlivka, where they are currently examining the accident scene, seizing documents, questioning witnesses etc., Deputy Prosecutor General of Ukraine Anatoliy Pryshko said at a briefing in Horlivka on Wednesday.

Commenting on the causes of the accident, he said that "a crack appeared in an ammonia pipeline, and ammonia escaped, hitting people." Pryshko added that there was no immediate environmental threat to local residents and the city.

According to him, 22 people injured as a result of the accident are currently in hospital, with eight of them in a serious condition.

The deputy prosecutor general said that criminal proceedings were launched under Part 2 of Article 272 of the Criminal Code (violation of safety rules during the execution of hazardous work that caused the loss of life), which is punishable by up to eight years in prison. At the same time, the matter of bringing charges against any of the company's employees will be raised only after the expert commission makes its conclusions, Pryshko said.

According to the deputy prosecutor general, the Interior Ministry is conducting an inquiry into the accident. At the request of Prosecutor General Viktor Pshonka, a task force which includes representatives of the Interior Ministry and the Security Service of Ukraine has been set up to establish the cause of the accident, Pryshko said.

Asked whether the management of the Stirol Concern tried to conceal the information about the accident, the deputy prosecutor general said: "Indeed, the report about the incident did not immediately reached law enforcement agencies, and now we are establishing why this happened."

As reported, an ammonia blowout occurred during overhauls at the No. 1 Plant of PJSC Stirol Concern on August 6. Five people were killed, 22 hospitalized with various injuries, nine of them were taken to an intensive care unit.

According to preliminary findings, the gas leak occurred due to an ammonia pipeline failure.

Stirol is one of Ukraine's biggest chemical producers. Ostchem is a managing company that coordinates the strategy of six fertilizer companies belonging to Group DF of Dmytro Firtash, four of which are located in Ukraine: Stirol Concern, Severodonetsk Azot, Cherkasy Azot and Rivneazot.