A saw-scaled viper, considered one of the deadliest snakes in the world, travelled to the UK in a shipping container carrying rocks from India.
Vets from South Essex Wildlife Hospital rescued the reptile after a stonemason, who had ordered the rocks, called the hospital for help.
"The snake was probably cold from travelling, so was not too active," the charity's founder and manager Sue Schwar was quoted as saying by the BBC. Those who opened the crate and found the reptile were "very lucky to be alive", she said.
“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,” the charity added.
The snake is being kept in a room where the door has been taped up with warning signs.
The saw-scaled viper is found close to inhabited areas in south Asia, Africa, and the Middle East.