UK families are awaiting news of relatives in Saudi Arabia, following the fatal stampede near Mecca.
British Muslims have told the BBC they are worried about people who made the pilgrimage and have not been heard from since Thursday's incident, in which 717 people died.
The Foreign Office said it was seeking information from Saudi authorities on any Britons who might be affected.
Anyone worried about friends or family can call a helpline on 020 7008 1500.
So far no British nationals have been confirmed among the dead following the incident, which happened at Mina as two million pilgrims took part in the last major rite of the Hajj pilgrimage.
Saleem Kidwai, of the Muslim Council of Wales, has said he is aware of one group of pilgrims from Cardiff which has not so far made contact with home.
On Thursday Foreign Secretary Philip Hammond said UK officials were "checking hospitals and other locations to urgently gather information about British nationals who may require assistance".
Speaking to the BBC in East London earlier, one British woman, Amy, said most British Muslims would know someone attending the pilgrimage.
"Currently I have about, maybe, 10 friends over there, some of whom we're still trying to get hold of," she said.
She added that most people making the trip did not take their phones, as it was a "spiritual journey" - but as Saudi authorities were releasing details of the dead she assumed that "no news is good news".
British pilgrim Kashif Latif told the BBC he passed through the area "a couple of hours" before the tragedy happened.
He said he first heard something was wrong when loved ones in the UK phoned to make sure he was not hurt.
But he added: "We had seen a lot of skirmishes and a lot of close calls purely through the sheer volume of people that there are at the Hajj."
Rashid Mogradia, chief executive of the Council of British Hajjis (CBH), told the BBC the place where British pilgrims camp was "kilometres away from the main incident point".
"We have to take some kind of consolation to know that they are away from the actual incident place," he added.
The CBH estimates that more than 25,000 UK Muslims travel each year to take part in the Hajj, a five-day pilgrimage that every adult Muslim must perform at least once in their lives if they can afford it and are physically able.