Three boys aged eight, 10 and 11 died after falling into an icy lake in Solihull, police confirmed.
A fourth boy, aged six, remains in critical condition following the incident at Babbs Mill Park on Sunday afternoon.
A search is continuing after unconfirmed reports up to six children may have fallen, but authorities have warned it is ‘no longer a search and rescue operation’.
The four children were all in cardiac arrest when rescue teams pulled them out.
They were taken to hospital but police said three of them “could not be revived”.
Reports from the scene and social media videos indicate they were playing on the ice and fell, the fire department said.
Search teams were still using boats and wading in the lake on Monday – and police said they would continue until they were ‘100 per cent certain’ there were no other victims .
One of the first officers on the scene entered the lake in uniform and tried to break through the ice to help the boys, West Midlands Police Superintendent Richard Harris said.
Members of the public also took the plunge.
Firefighters and water specialist crews arrived at the lake and managed to get the boys out. They received CPR and were taken to hospital, but all four arrived in critical condition.
Police said it is currently unclear how long they were in the freezing water.
A witness told Sky News he saw firefighters breaking through the ice and a number of people in distress.
The names of the children have not yet been released and police have said they support their “absolutely devastated” families.
The boys’ classmates also receive support.
Teams in boats used torches to continue searching the lake overnight.
A police officer involved in the initial search suffered mild hypothermia and was taken to hospital, but has now been discharged.
Superintendent Harris said midday Monday they were still trying to piece together exactly what happened, but no one had contacted them to report anyone else missing.
But due to conflicting reports about the number of children who were on the lake, the search will continue until police are certain no one else has entered.
Local MP Saqib Bhatti visited the scene on Monday and praised the emergency services for their “heroic” efforts.
“The (search) operation lasted all night in these really difficult conditions,” he said, adding that “the whole community will feel the pain.”
Police asked people not to speculate or share any video of the incident.
Richard Stanton, zone commander for the West Midlands Fire Service, urged parents and carers to remind their children of the dangers of frozen water.
He said: “Please, adults and children, stay away from open water. Under no circumstances should you venture onto ice, no matter how thick or safe you think it is. this ice cream.”