A gas explosion in a new cafe in the heart of Sydney has left two staff in hospital with burns to their faces and chests.

A 23 year old Chilean sandwich hand, Camille, and the cafe’s 24 year old male head chef from Nepal were blasted when the grill exploded on Monday morning, while a third worker escaped uninjured.

The two injured have been taken to St Vincent’s Hospital.

Canadian salad bar worker, Alissa, 25, ducked to escape the “fireball”, which travelled half a metre through the narrow kitchen in the George St cafe.

It’s believed a gas grill started a small fire, which caused the explosion.

“I heard a really loud bang, and dived down but my hair got singed. I thought a canister had fallen onto the stove,” she said.

“My glasses were fogged up and I just got out of there.”

The workers were prepping for the lunch rush when the explosion occurred at the health cafe which opened three weeks ago.

Two customers were seated outside the cafe and about 10 staff were present when the explosion occurred.

Owner George Michaels told AAP he didn’t think “there’s that much damage”.

“Something just blew. The kitchen looks fine. I don’t know where this fire came from,” he said.

“I just feel bad (that) they got their faces burnt.”

Fire and Rescue NSW set up an exclusion zone.

“The fire crew has isolated the gas and are doing atmospheric monitoring to ensure it’s safe before personnel can enter the area to investigate the cause of this explosion,” a fire and rescue spokesman told AAP.

AAP