Police said the explosion occurred at a three-storey shophouse in Tambon None Phra in Rayong’s Mueang district at 9.10 am.

Three male Cambodian workers suffered severe burns as they cooked in the shop’s basement kitchen. The injured also included shop customers.

Shop owner Papatchaya Thirapaspipat, 45, said the explosion occurred when one worker turned on a microwave oven. She said the explosion might be caused by leakage from the cooking gas cylinder.

The whole kitchen room was damaged and the impact caused the concrete wall at the back of the shop to be hurled three metres.

Authorities sealed off the building pending a structural safety check.

Forensic science police have yet to confirm the cause of the explosion.