Four children were taken to hospital in critical condition after being rescued from an icy lake near Birmingham.
They have been taken to two hospitals in the city after the incident at Babbs Mill Park in Kingshurst on Sunday afternoon.
West Midlands Ambulance Service said there was no update on their condition.
The Met Office has warned of the dangers of ice, as a cold spell in the UK is expected to continue for days.
During a news conference on Sunday evening, West Midlands fire chief Richard Stanton said: "We have continued search operations in order to confirm whether there were any more in the water."
He said crews were told on arrival that up to six people were in the lake.
Mr Stanton added: "The specialist medical advice we have been given on the scene, given the temperature of the water, given the age of those who entered the water and the amount of time they have been in there, this would no longer be a search and rescue operation."
The ambulance service said its resources had now been stood down.
Supt Richard Harris, of West Midlands Police, said during the news conference that his officers would "hold the scene tonight", but he could not confirm they were looking for anyone else at this stage.
He said one officer had suffered "mild hypothermia" during the rescue operation, but was making a recovery after being taken to hospital "as a precaution".
All three emergency services said they were called shortly after 14:30 GMT on Sunday, with the first ambulance arriving within seven minutes after it was called.
Temperatures of 1C (34F) were reported in the area at the time. They are expected to plummet to -3C during the night.
The UK is expected to continue experiencing a cold spell - with snow, ice and freezing fog expected for days, according to forecasts.
Temperatures could drop as low as -15C (5F) in northeast Scotland overnight, which would be the lowest temperature recorded in the UK since February last year.
The four children were pulled from the lake in cardiac arrest, said Cameron McVittie, a tactical commander with the West Midlands Ambulance Service.
He said they received immediate treatment on site, before being taken under blue lights to hospital with an advanced care team.
"Two were taken to Birmingham Children's Hospital and two to Heartlands in Birmingham," Mr McVittie said.
He added: "There are no updates. They were all in critical condition when they arrived in hospital."
The officials declined to provide any further information about the children involved in the incident.
Concerned members of the community had gathered near the scene in a residential area, as emergency services worked at the lake.
A drone was also spotted flying over the water.
Babbs Mill Park is a local nature reserve with a lake, river, wildflower grasslands and woodlands.
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Local MP Saqib Bhatti said he was being updated on the situation, and that his "thoughts and prayers are with the whole community".
The Met Office warned of the dangers posed by ice during the UK's cold spell.
A spokesperson said: "With temperatures set to struggle to get much above freezing over the coming days across much of the country, stretches of water such as rivers and ponds are at risk of freezing.
"While frozen rivers and ponds can be fascinating, they can be dangerous and a hazard to life."
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