The explosion occurred along the Urengoi-Pomary-Uzhgorod gas pipeline in the Poltava region around 2:00 p.m. local time. No one was injured.
Ukrainian Interior Minister Arsen Avakov announced via the ministry website: "An Interior Ministry operational team is conducting investigative actions to determine the causes of the blast. Several theories of the incident are being explored, including the key theory of a terrorist attack."
The interior ministry said that "a major disaster" had been averted after authorities shut down the gas supply to the pipeline and extinguished the fire.
Svitlana Rybalko, a spokeswoman for the Poltava State Emergency Situations Service, told Interfax-Ukraine that the explosion was caused by a loss of pressure. Sabotage has not been ruled out.
In response to Tuesday's explosion, Naftogaz Ukrainy --Ukraine's national oil and gas company -- said it will tighten security along the gap pipelines.
Naftogaz head Andriy Kobolev wrote via Facebook, "The situation is very alarming. It was a very strange coincidence of circumstances. We will do all we can to tighten security at all of the gas transportation systems' facilities."