Three people, including an expert in controlled explosions from South Korea, were killed and at least four persons were injured when they were trying to defuse detonators that had misfired at the site of the under-construction petroleum reserve for the country on Thursday evening, near here.

The Korean has been identified as Mr. Song, according to a source.

The other two dead were Sirajuddin, Safety Officer, and a labourer.

The underground cavern project is being executed by Indian Strategic Petroleum Reserve Ltd. (ISPRL) to store crude oil with enough stocks to last 15 days during emergencies.

Rajan Pillai, the Delhi-based CEO of ISPRL, said the experts were handling explosives outside the cavern and not inside.

“Normally a huge amount of precaution is taken and I am surprised it happened. “It is unexpected and unfortunate.” A reliable source said the Korean mining engineer had previously handled two projects in Korea that were larger than this.

The injured include two mining engineers and a safety officer and a labourer.