One of the world's deadliest snakes found in shipping container sent from India

South Essex Wildlife Hospital received a call from a local British stonemasonry firm about a long, spotted snake they found in a shipping container from India.

Turns out, the snake is a saw-scaled viper, one of the deadliest snakes in the world, according to South Essex Wildlife Hospital on Twitter. South Essex Wildlife Hospital is a wildlife rescue, treatment and rehabilitation charity​ in the U.K.

While most snakes are harmless to humans, the saw-scaled viper is a dramatic exception.

"It's dangerous because it's not native to us. It comes from India. They're highly venomous, and they're very, very aggressive." says Sue Schwar, founder and hospital manager of the South Essex Wildlife Hospital.

The saw-scaled viper is the smallest of the "Big Four" snakes, the four species of snake that cause the most deaths annually worldwide, according to AnimalResearch.info, a resource created by a U.K. not-for-profit organization focused on humane animal research.

"Because, they're small, they're more aggressive, they bite more people. As far as kill rates, they kill more people than other bigger snakes do," Schwar says.

If you're bitten, the venom could kill you unless you get access to an antivenom. Even with the antivenom, the toxins in its bite break down our ability to form blood clots, causing many survivors to intensely bleed and lose their limbs, according to National Geographic.

Schwar points out that it's especially dangerous to find them in Britain because most snakes from the region are harmless, so hospitals are not equipped with the antivenom needed to treat people bitten by these deadly snakes.

►Snakes in grocery stores: 10-foot-long python slithers across grocery store shelves, curls up behind spices

Lucky for the British workers, the snake spent weeks on end in a chilly container, which likely subdued it since reptiles need warmth to be active, CNN reports.

South Essex Wildlife Hospital sent a reptile expert and vet to collect the specimen, and they put the snake in a locked box in a sealed room. To be extra careful, the vet taped the door shut. Several warning signs have also been placed on the door.

"We are glad not to have to deal with venomous creatures too often but feel sad for the snake that we can't give it is freedom and get it back home," said the South Essex Wildlife Hospital on Twitter.

It's not the first time the wildlife charity has found one of these snakes in Britain, Schwar says. Years ago, they found the exact same species, also in a stonemason's shipping container from India. The wildlife hospital followed a similar process of locking the snake up and securing the room. More experienced wildlife experts then came to pick up the snake and bring it to its new home.

The snakes are always kept alive, says Schwar, unless "it was injured, and we couldn't apply any veterinary care for it because it's too dangerous to handle."

Killing the snake would always be the "last resort," Schwar said.

Follow Michelle Shen on Twitter: @michelle_shen10.

This article originally appeared on USA TODAY: Deadly snake found in shipping container: Viper in England from India