On 4 August, a massive blast devastated the Beirut port area.

A huge store of ammonium nitrate in a warehouse is thought to have been the cause of the explosion. 

Who knew about the dangerous cargo and who is to blame for the destruction it unleashed?

First, the ground shook, ever so slightly, almost imperceptibly. A quick look around confirmed the sensation; the wardrobes in the house were shaking. 

One second, two seconds, three, and it stopped. A moment of stillness, and then it struck – an earth-shattering blast.

This time the whole building shook, but that was nothing compared with  the sound. And this was more than 10km from the site of the blast in Beirut. 

An instinctive rush to the windows to see smoke billowing from the direction of the capital. Then, an instinctive rush away – what if there was another one?

For many, it was the loudest explosion in memory, and there’s no shortage of explosive memories in Lebanon.

On the highway into Beirut from the north, ambulances inched their way through heavy traffic – a stream of motorists desperate to get to the surrounding neighbourhoods, check on friends and relatives, and take them away. 

On the opposite side, cars sped in the other direction, making their escape from the inferno. 

With traffic at a standstill, radios and phones brought the most terrible news – of hospitals overwhelmed, of thousands injured, and of the raging fire.

Those driving towards Beirut were forced by the army to make a U-turn, or continue on foot if they chose. 

Broken glass crunched underfoot on the last stretch of road before entering the city, and a tractor roared through, clearing piles of rubble. 

Buildings were barely recognisable, with empty window frames and no lights in sight.

A few silent figures emerged from the dark, some wounded but walking, others sitting and waiting with empty stares and barely a sound. The closer to Beirut, the darker it got.

It had started with a fire in the port. Even now it’s not clear the precise time the blaze started.

But by 17:54 local time, a tweet from a correspondent for the Los Angeles Times showed the smoke billowing into the sky.  

What followed has been shown in a series of videos posted on social media. There is an initial explosion which throws denser, darker smoke and debris into the air. 

A series of flashes can be seen, almost like fireworks going off. An intense area of flame can be seen at the base of the smoke. 

Then, 35 seconds after the first blast, there is a second, massive explosion. A huge column of red/brown smoke goes up and a white dome-like cloud follows the blast out.

Scores dead. Thousands injured. The heart of a city destroyed.

And at the centre of it, a warehouse full of nearly 3,000 tonnes of a chemical used for explosive. Ammonium nitrate.

The photo is from summer 2014. Two men stand smiling on the deck of an unremarkable looking cargo ship in Beirut Harbour. Innocuous looking white sacks are stacked in the hold behind them.

The sacks contain nearly 3,000 tonnes of high-density ammonium nitrate. One man, in blue, slightly squinting into the camera, is on the phone. 

He was a man with a lot on his mind. By that point Captain Boris Prokoshev and several of his crew had been stuck in the port for months.

The ship, the MV Rhosus, had set out from Batumi, Georgia, in late September 2013, apparently destined for Beira, in Mozambique. 

Built in 1986, the Rhosus was getting old. On trips around the Mediterranean earlier in the year, she had fallen foul of inspectors. In July 2013, at the port of Seville, inspectors found 14 separate deficiencies, from corroded decks to poor fire safety.

From May 2012, it had had a new owner, Igor Grechushkin, a Cyprus-based Russian businessman. According to business contacts, the MV Rhosus was Grechushkin’s first foray into running his own ship.

In Batumi, the bill of lading – the document acknowledging receipt of cargo – lists Rustavi Azot LLC as the company supplying the ammonium nitrate and says the customer is the International Bank of Mozambique, acting on behalf of a small Mozambique firm specialising in the manufacture of commercial explosives.

Prokoshev, who says he joined the Rhosus as captain in Turkey, has told the BBC it was soon apparent there were major problems.

The ship’s original crew had left, he said, claiming they hadn’t been paid for four months.  According to Prokoshev, when the ship and its new crew arrived in Athens, food and other goods had to be returned to suppliers because the owner said he couldn’t afford to pay for them.

The ship spent four weeks there while the owner hunted for additional cargo to pay transit fees through the Suez Canal. Eventually, this resulted in a fateful detour to Beirut.