An explosion in late September at a refinery in coastal Thailand designed to recycle used motor oil left two workers dead, the Thai publication The Nation reports.

The blast, which occurred during an equipment test on September 29, collapsed portions of the recently completed GRD Energy oil refinery in Samut Sakhon.

A company official said it is suspected that pressure built up in a joint connecting an 800-liter oil tank to a chamber that heats the oil to more than 200 degrees Celsius, leading to the explosion.

Firefighters extinguished the resulting blaze within 20 minutes.

The two refinery technicians killed were standing in front of the oil tank, the company stated. No other injuries were reported.

Damage was estimated at the equivalent of $320,000 U.S. dollars.