Police and specialist wildlife officers are using boats and a drone to search a stretch of river in north-west Spain after three sightings of what is thought to be a Nile crocodile. People in and around the towns of Simancas and Tordesillas in the Castilla y León region have been told to stay away from the banks of the Pisuerga River while the search continues. Francisco Sánchez, a police officer in Simancas, saw the animal at 2pm on Saturday as he followed up earlier reports. “It was a crocodile that measured between 1.5 metres and 2 metres,” he told the Guardian. “I saw it move through the water before it disappeared under the surface. I’ve never been that close to a crocodile before; it was kind of stomach-churning.” Sánchez said officers from the Guardia Civil’s wildlife division, Seprona, had cordoned off the area and were continuing the search. “The theory is that someone was keeping it in their home and that they released it when it got too big,” he added. The region’s emergency services said they had received reports of the animal over the weekend. “We get all kind of calls, but the one we got at 14.27 today has surprised us,” 112 Castilla y León sad in a tweet on Saturday. “Local police from Simancas and Seprona have been mobilised to find a crocodile that has been seen where the Duero and Pisuerga rivers meet.” Warning bulletins have been issued as the hunt goes on. “We have been informed of the existence of a dangerous animal close to the town,” Simancas town hall said in a statement. “Given the possible threat to people, we are asking residents and walkers not to swim or get close to the riverbank. Special care must be taken until the animal has been captured.” Sánchez said people in Simancas were “a bit nervous”, adding: “It’s a popular fishing and swimming area and people don’t want to believe it’s there.” Nile crocodiles, which can grow up to 6 metres in length and weigh as much as 750kg, are found in rivers from Egypt to South Africa. According to some estimates, they kill about 200 people each year.