11-Year-Old Boy Disappeared in River as Police Say Family Is Living ‘Every Parent’s Worst Nightmare’

U.K. police are still searching for an 11-year-old boy who was last seen entering the River Don in Mexborough, England, on Saturday, May 30.

Police were called to the scene shortly after 8 p.m. local time, South Yorkshire Police wrote in a statement on social media. On Monday, June 1, police identified the missing person as 11-year-old Mackenzie Swift, who had entered the river near Ferry Boat Lane.

South Yorkshire Fire and Rescue Service, Woodhead Mountain Rescue and an underwater search team all contributed to search efforts, according to South Yorkshire Police’s statement.

“While we are doing everything we can to find him, our Family Liaison Officers have sadly had the heartbreaking conversation with Mackenzie’s family that if he had not exited the river on Saturday, he could not have survived in the water for this length of time,” South Yorkshire Police said. “Sadly none of our enquiries so far have found any indication that he got out of the water.”

“We will continue to do everything in our power to find Mackenzie and to support his family through this incredibly difficult time,” Doncaster District Commander, Chief Superintendent Pete Thorp said in a statement. “They truly are living every parent’s worst nightmare.”

Thorp added that officers and rescue teams around the region would remain at the search site Monday evening and “further operational activity” would continue early Tuesday morning, June 2.

Thorp asked concerned locals to “leave this work to the professional search teams” and not to enter the dangerous waters in an attempt to locate Mackenzie’s body.

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“Please do not put yourselves or others in danger by searching in and around water, and if asked to leave by officers, please understand this is for your own safety and to ensure our efforts focus solely on finding Mackenzie,” Thorp said, adding that the “thoughts of all those involved in the extensive search operation remain with Mackenzie and his family.”

PEOPLE has reached out to South Yorkshire Police for updates.