LONDON — A fire tore through a 24-story West London apartment building early Wednesday, killing at least 30 people and injuring more than 70. The authorities said that the death toll was expected to rise, and that some bodies might never be identified.

The police have begun a criminal investigation into the circumstances surrounding the blaze, but said there was nothing to suggest the fire had been deliberately set.

How did the fire start?

The fire was first reported at 12:54 a.m. The site was Grenfell Tower in North Kensington, built in 1974, which housed at least 400 people in 120 apartments across 20 residential floors. Firefighters responded within six minutes. The blaze began on the fourth floor and spread to the top with a velocity and intensity that stunned the 250 firefighters who responded. Pockets of fire were still blazing on Thursday morning, more than 24 hours after the fire broke out.