Stunned residents in Iran's north-east have begun burying more than 300 people killed when a runaway train exploded.
Relatives are searching the charred bodies to find their loved ones
The thunderous blast killed everyone at the scene, and wiped out at least five nearby mud brick villages.
More than 20,000 residents of Neyshabur town turned out for the funeral of local Governor Mojtaba Farahmand-Nekou, one of several officials at the scene.
As local Red Crescent officials said the death toll was on the rise, the government ordered an urgent inquiry.
"There are 320 dead and 460 injured so far," said Ali Hosseini, head of the Red Crescent in Khorasan province, the scene of the blast.
"But many are still under rubble and we are expecting the death toll to rise."
There was a grim stench of unclaimed bodies in the cemetery of Nishapur where limbless torsos and body parts had been laid out on plastic sheeting, Reuters news agency reported.
Mothers were sifting through the charred bodies looking for enough evidence of their loved ones for a fitting burial.
"The magnitude of the explosion means that identifying the bodies will be a very slow process," said Mehran Bakili, local chief coroner.
In Neyshabur, survivors looked through lists of the dead posted outside hospitals and clinics.
Alireza Babaie, who said he was in his 70s, said he was looking for the name of a friend who had been travelling to visit him from the provincial capital, Mashhad, 75km (50miles) away.
"His family said he was on his way, and he should have reached here by now. I don't know where he is, and I hope to God he is not among the dead," he said.
As the city's shops and offices closed for three days of mourning, more than 20,000 people wearing black looked on as the body of Governor Farahmand-Nekou - wrapped in a red, white and green Iranian flag - was driven through the city.
WORLD'S WORST TRAIN DISASTERS
June 2002: Dodoma region, Tanzania - at least 200 killed when passenger train collides with goods train
Feb 2002: Egypt - 300 killed in fire on train travelling to Cairo
June 1989: Ufa, Russia - More than 400 killed in gas explosion under two trains
Aug 1995: Uttar Pradesh, India - 300 killed in train collision
June 1981: Bihar, India - 800 killed when cyclone blows train into river
On Thursday, relief workers were finally able to start sift through the debris - after being kept back overnight for fear of further explosions - and used bulldozers and cranes to lift the wreckage.
A team of experts are also determining the health hazards from the fumes, said Hassan Rasouli, governor of Khorasan province. Many residents have been complaining of severe sore throats.
The blast occurred after 51 train cars - laden with sulphur, petrol, fertilisers and cotton wool - broke lose and rolled about 20km (12 miles) down the track.
The wagons derailed at Khayyam station near Neyshabur and caught fire at 0400 (0030 GMT) on Wednesday.
As firefighters were attempting to douse the flames - watched on by crowds of curious villagers and officials - the train exploded, at 0935 (0605GMT).
The blast was so powerful that local residents thought it was an earthquake - and Iranian seismologists recorded a quake of magnitude 3.6 at the time of the explosion.
"The entire area around me shook," said Hussein Hassani, who was several kilometres away at the time.
"It felt like a strong earthquake, but because the buildings didn't collapse (where I was) I knew it wasn't. Smoke could be seen... for hours."
Relief workers are starting to sift through the wreckage
The clay-home village of Dehnow, which was closest to the blast at about 550 metres (500 yards) away, was flattened and many villagers were believed to have been killed. The rest are thought to have been evacuated.
Casualties were also found in other nearby villages where buildings had collapsed. Some of those injured were either burned or hurt from the force of the blast, said hospital officials.
It is still unclear what caused the heavily-laden freight train to derail.
The government ordered an immediate inquiry into the disaster and has demanded the results by Sunday.
Officials want to know how the freight wagons, which were not attached to a locomotive, could have simply moved off down the line, eventually careering off the track and bursting into flames.
They are also demanding to know why the train - which was said to be on its way from central Asian countries to Iran's southern port of Bandar Abbas - was loaded with such a lethal combination of chemicals.
Iran is still recovering from a devastating earthquake on 26 December in the ancient city of Bam in the south-east of the country, in which more than 40,000 people died.
Have you been affected by the train disaster? Send us your stories.
My cousin was on the train from Tehran to Mashhad, next to the fired train, and they were stopped at Attar station for about 1 hour, then a guy shouted and asked people to leave the train and to keep distance as much as they could, they all started to running out and after 5 minutes an awful explosion happened which caused them to fall down.
My cousin said it was just like what I've seen before in movies about the explosion in Hiroshima! She is still in shock and feels that her lungs are filled with tar.
Bahar, Mashhad, Iran
My cousin, Henry Falsun is living in the city of Neyshabur. When I learnt about the disaster, I immediately phoned Henry. He told me that he had heard an explosion and that in his city there wasn't any damage.
George Falsun, New York, USA
It was very terrible; I think the number of the victims will become more than 200. It happened in the north east corner, near the major city of Mashhad. The thing is it has happened when it is just 2 days to a great election here and this happen has shocked all the country.
Ali Emami, Shiraz/Iran
This blast is a miserably unfortunate incidence. I feel sorry for all the families that are facing it. The chemicals and toxic fumes in the air carry a potential danger for the inhabitants. I congratulate the people of Iran for showing strength and courage in this hour of mishap. May God bless all.
Shubham Basu, Nashville, USA
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