At least 192 people are missing and 75 are dead as a result of the explosion of the Fuego volcano in Guatemala on Sunday, officials say.
Villages on the slopes were buried in volcanic ash and mud.
Rescue work on Tuesday was disrupted when a new eruption sent hot gas and molten rock streaming down the volcano’s south side.
More than 1.7 million people have been affected by Sunday’s eruption, with more than 3,000 evacuated.
Tuesday’s explosion took many by surprise after volcanologists said the eruption, which had sent ash up to 10km (33,000ft) into the sky on Sunday, was over for the near future.
Eddy Sanchez, the head of Guatemala’s National Institute of Seismology, had predicted “no imminent eruption over the next few days”.
Why were so many people killed in the initial eruption?
“We now have an accounting with names and towns where people have gone missing and we have a figure, which is 192 people who we have unaccounted for,” Disaster Relief Agency chief Sergio Cabanas was quoted as saying by AFP news agency.
Figures for the dead were tweeted by Guatemala’s National Institute of Forensic Sciences (Inacif).
No evacuation alert was issued before the volcano erupted on Sunday, said Sergio Cabañas, the director of Guatemala’s disaster prevention agency.
He said that local residents had received training in emergency procedures but were not able to implement them because the initial volcanic activity happened too fast.
Sunday’s blast generated pyroclastic flows – fast-moving mixtures of very hot gas and volcanic matter – which descended down the slopes, engulfing communities including El Rodeo and San Miguel Los Lotes.
Volcanologist Dr Janine Krippner told the BBC that people should not underestimate the risk from pyroclastic flows and volcanic mudflows, known as lahars.
“Fuego is a very active volcano. It has deposited quite a bit of loose volcanic material and it is also in a rain-heavy area, so when heavy rains hit the volcano that is going to be washing the deposits away into these mudflows which carry a lot of debris and rock.
“They are extremely dangerous and deadly as well.”
‘Like black rain from the sky’
Londoner Faye Dunstan, manager of the Oxford Language Centre in Antigua, close to Fuego, described for BBC News the day the volcano erupted.
“We were just sitting at home and then suddenly there was rain from the sky but it was black and it was lava ashes,” the 29-year-old said. “No one really thought it was a big deal so everyone was out taking selfies.
“But then we were driving and the police were stopping everyone from driving… People were coming out of their houses and restaurants to hose down all of the cars. There was lava ash everywhere.
“But still no one really realised that it was that bad of a situation until later on Facebook when the news kept coming in. It started with seven people dying. The number rose to 25 and then 33.
“In Antigua [a local city in Guatemala] people are collecting donations on street corners. Everyone has lava ash in their hair. There are schoolchildren everywhere because the schools are closed.
“People in neighbouring villages are scared there will be an aftermath, but everyone is coming together. There are endless supplies of water, food and clothes. It’s a big community effort.
What is a pyroclastic flow?
A pyroclastic flow is a fast-moving mixture of gas and volcanic material, such as pumice and ash. Such flows are a common outcome of explosive volcanic eruptions, like the Fuego event, and are extremely dangerous to populations living downrange.
Just why they are so threatening can be seen from some of the eyewitness videos on YouTube of the Guatemalan eruption. In one, people stand on a bridge filming the ominous mass of gas and volcanic debris as it expands from Fuego.
Some bystanders only realise how fast it is travelling as the flow is almost upon them.
The speed it travels depends on several factors, such as the output rate of the volcano and the gradient of its slope. But they have been known to reach speeds of up to 700km/h – close to the cruising speed of a long-distance commercial passenger aircraft.
In addition, the gas and rock within a flow are heated to extreme temperatures, ranging between 200C and 700C. If you’re directly in its path, there is little chance of escape.
The eruption of Vesuvius, in Italy, in 79 AD produced a powerful pyroclastic flow, burying the Roman towns of Pompeii and Herculaneum under a thick blanket of ash.