Post-mortem examinations of the bodies of two women found in a hotel room are expected to confirm a double suicide.
The women, one aged in her 30s, the other in her 50s, were found in a bedroom of the Costello Palace Hotel in Finsbury Park, north London.
The discovery of a powder in the room prompted police to evacuate the hotel and close off roads in the surrounding area, in what emergency services described as a chemical incident.
A police spokeswoman said the women "are believed to have committed suicide by taking a noxious substance".
Officers from London Fire brigade were seen entering the building in decontamination suits and specialist breathing apparatus.
At the height of the operation more than 15 emergency service vehicles were clustered outside the hotel.
Guests staying at the hotel said they thought the bodies of the women had only been discovered late on Sunday morning.
Graham Cannon, 43, from Halstead, Essex, visited London on Saturday to watch a music concert.
He explained: "We came down for breakfast this morning at about 8.30 and it was absolutely packed. Nothing seemed wrong at all then. We were laughing and joking with the manager. Everything was normal. You don't have to check out of here until 11 so I suppose the staff didn't even find the bodies until after then."
Eileen Early, 43, from Great Dunmow, Essex, added: "It's just awful when you think about it. It's such a shock to realise that this has gone on while we were inside the hotel."
