At least four Britons are now understood to have been killed in the New Zealand earthquake, the Foreign Office has said.
Two more British people are injured and one remains missing, a spokesman added.
One of those killed was previously named as Gregory Tobin, a 25-year-old chef, from Tadcaster, North Yorkshire.
Tuesday's magnitude 6.3 earthquake in Christchurch killed at least 148 people and about 50 are still missing. A UK rescue team is still working there.
A helpline on 020 7008 8765 has been set up for concerned friends and relatives in the UK.
British nationals in New Zealand are advised to call 049 242 898 for advice and assistance. The Foreign Office website has more information about the consular assistance being provided.
Victims of the quake that devastated the centre of Christchurch have been honoured at church services across New Zealand on Sunday.
The country's Prime Minister John Key said there was still a glimmer of hope survivors could be found.
But no-one has been found alive since Wednesday, and rescuers working for a fifth day are only finding bodies.
The British High Commission had earlier said two UK victims had "got on a certain bus, which was crushed by falling masonry".
Mr Tobin had been on a round-the-world trip and had been working at a restaurant in Christchurch.
One of the tributes to him on Facebook read: "Such a nice guy and at such a young age."
Jo Morley, 44, whose brother Phil Coppeard from Bury St Edmunds in Suffolk was reported as missing, told the BBC on Saturday the family still had hope he would be found alive.
She said: "Of course you still hope, as anybody would do. That's what we have to think."
Chartered accountant Mr Coppeard, 41, emigrated to the country in November with his wife Suzanne Craig and was doing a masters in economics at the University of Canterbury in Christchurch.
He was travelling into the city centre on a bus when the earthquake struck.
British High Commission spokesman Chris Harrington said the two injured Britons were a man and a woman, both aged over 50. Their injuries were serious, but not life threatening.
The man is still in hospital but the woman, who lives in Christchurch, has been discharged.
A British team of experts in identifying disaster victims is due to arrive in the city tomorrow.
Meanwhile, tributes have been paid to Irishman Owen McKenna, originally from Emyvale in County Monaghan, who died in the quake when his car was crushed by falling debris.