The migrant dinghy in which five people died was chaotic, overloaded and packed with people carrying weapons and fighting, according to one of the passengers who was on board, speaking exclusively to Sky News.
Heivin, 18, confirmed the boat was stormed by a rival group of migrants, armed with sticks and knives, as it was preparing to set off.
She said: "People were fighting, people were getting stepped on, they were dying and being thrown off."
She said she fell into the water but was pulled out by another person on the boat. Two other passengers who fell into the water, including a young girl, drowned. Three other people died on the boat.
Heivin said she "really hated" the group of people who hijacked their boat, insisting they should take the blame for what happened.
"They caused a huge tragedy," she said.
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"It was because of them that people died.
"If they hadn't come and started fighting, none of this would have happened."
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The tragedy happened in the early hours of Tuesday morning in the waters off the French coastal town of Wimereux.
The boat, which launched with 112 people on board, stopped on a sandbar only a few hundred metres from the shore.
By the time emergency services arrived, it was clear people had died, both on the boat and in the water.
Two men have been charged with immigration offences in connection with the investigation into the deaths of the five migrants.
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"I fell into the water but a man helped me up," Heivin said.
"Everyone was climbing aboard and there were too many people - over 110 of us.
"I had tried to be at the front, but after I fell in the water I sat on the edge of the boat and didn't go towards the other end - that's where people were fighting.
"I thank God that I didn't get into the top part of the dinghy. I would have suffocated. I thank God for that every day."
She said her group, comprising between 50 and 60 people, had arrived at the beach in Wimereux after following the instructions of the people smugglers who had taken their money in exchange for arranging a passage to Britain.
Hidden away, they had waited for the smugglers to prepare the dinghy. She then saw police officers and was told simply to run towards the water.
At that point, the rival group emerged as well, clambering into the boat along with the people who had paid the smugglers.
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Heivin said she saw migrants from this group carrying sticks and knives, squaring up to both the police and the original passengers.
When the boat set off, exceptionally overladen, it meandered towards the Channel, but there was still fighting and it is clear that some people were being crushed.
"I was aware there was a fight," Heivin said.
"They were shouting that people were stuck underneath other people, that they couldn't get out, that some were falling under people's feet."
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Heivin has spent seven months travelling across Europe since leaving Iraq. She said she wanted to get to Britain because "it is a better country for me, definitely in terms of the language but also, in many other other ways, it is better than the rest of Europe".
She's made 30 attempts to cross the Channel, but has failed each time. Sometimes it has been the French police who have destroyed boats while other times the boat on which she was travelling broke down. One time, the boat failed only an hour from British waters.
She is undeterred by the trauma that she underwent, however, and she intends to try again to reach Britain as soon as possible. "Perhaps this weekend," she said.
