At least 58 people are feared to have died in the fire that engulfed a London tower block this week.
With anger mounting over the government's handling of the blaze, Mrs May met residents from the Grenfell Tower and vowed to personally oversee the recovery as protesters gathered to demonstrate in the streets around her residence for a second day.
Weakened by a botched election gamble last week, May has been criticised for her muted response to the fire and had to be rushed away from a meeting with residents on Friday under heavy police guard as protesters shouted "Shame on you".
"The response of the emergency services, National Health Service, and the community has been heroic," May said in a statement.
"But, frankly, the support on the ground for families who needed help or basic information in the initial hours after this appalling disaster was not good enough."
London Police Commander Stuart Cundy said the toll of 58 represented those who were missing and presumed dead from a fire which ripped through the 24-storey social housing block as residents slept in the early hours of Wednesday morning.
"Sadly at this time, there are 58 people who we have been told were in Grenfell Tower on the night that are missing and therefore sadly I have to assume that they are dead," he said.
If the number is confirmed, it would make the Grenfell Tower blaze the deadliest in London since World War Two.
The toll had previously been put at 30.
Enter a name and e-mail address and we will e-mail this website link too them.