LONDON (AP) — British authorities are studying samples of similar to that used on the west London apartment building that caught fire, killing at least 79 people.

Eleven buildings have now been identified as having combustible cladding such as that used on the Grenfell Tower. The cladding is being studied amid fears that the panels fueled the fire in the 24-story building that was engulfed in less than an hour.

Buildings in London, Manchester and Plymouth are among those where problem cladding has been identified.

Fears about cladding is not limited to apartment buildings, and at least one hotel chain is calling in experts to make certain it meets safety regulations. Premier Inn said Friday it had “concerns” about the material on some of its buildings, though it is different to the type used on Grenfell.