Six people have died after a residential building collapsed following an explosion in a tourist area of central Athens, a Greek fire brigade official said on Saturday.

The victims have been identified as four American tourists and an elderly couple from Greece

The blast on Friday destroyed a two-storey building in Plaka, near some of Athens’ most visited sites including the Acropolis and the Temple of Zeus, injuring three people, damaging nearby houses, shops and cars and sending rubble and broken glass as far as three blocks away.

Household items and clothing were strewn amid the debris.

“It (the rescue operation) is not easy as the biggest part of the building has collapsed and there is risk for adjacent buildings which have been evacuated for security reasons,” police spokeswoman Constantina Dimoglidou told public broadcaster ERT on Saturday.

The tourists – two American couples – were expected to check out to catch a flight from Athens airport at 3 p.m. on Friday but didn’t show up, a police source said.

It was not immediately clear what caused the blast in an area which is home to many hotels and short-term rentals. Athens mayor Haris Doukas said on Friday it was likely linked to gas infrastructure. “Something went terribly wrong.”