An explosion that occurred Friday at a petrochemical plant at the Yeosu Industrial Complex in Yeosu, South Jeolla Province has claimed the lives of four people and injured four others. 

The explosion occurred at around 9:26 a.m. and did not lead to any ensuing fires.

Firefighters are combing through the site of the blast to determine whether the explosion caused any more casualties.

Authorities suspect that the explosion was a result of pressure being applied in the process of test-running heat exchangers.

The same plant experienced an explosion back in October 2001 which killed one person.