There were more than 200 excess deaths unaccounted for by Covid-19 in Hull and East Yorkshire in April, according to new local data analysis.
The deaths have not yet been registered as officially positive for Covid-19, but the numbers support concerns that the coronavirus-related death toll may be much higher than first thought.
The analysis of the deaths in Hull and the East Riding was carried out by data company Urbix using figures from the Office for National Statistics (ONS).
In Hull, there were 63 officially recorded Covid-19 deaths in April, while the five-year average number of deaths for the month, taken from the figures from 2015 to 2019, was 213.
Adding the deaths directly attributed to the Covid-19 pandemic to the average number of deaths for the month would therefore result in the expected number of deaths for April 2020 - a figure of around 276 deaths.
But there were 335 deaths in Hull in April this year.
Similarly, in the East Riding, there were officially 125 Covid-19 deaths in April, while the five-year average number of deaths was 323.
This would mean that, adding those together, the expected number of deaths for April 2020 in the East Riding would be around 448 deaths.
But there were 606, meaning Covid-19 only officially accounts for around 44 per cent of the excess deaths.
For Hull and East Yorkshire there were therefore around 217 deaths unaccounted for.
Urbix also extended the data to include March and May.
In that time period, the five-year average number of deaths in Hull was 557, while there were 127 Covid-19 deaths in that time this year - a sum of 684.
But there were actually 789 deaths in that time - an excess of around 100 deaths.
In the East Riding, the average number of deaths for that same period was 877, while there were 215 officially recorded Covid-19 deaths - to an expected total of around 1,092.
But there were actually 1,332 deaths in that time, an excess of nearly 250 deaths.
It is not clear what has caused this spike, but it is a pattern that has been replicated across the country, where the number of excess deaths in the months since the pandemic started has been far higher than the number of officially recorded Covid-19 deaths.
It raises the question of why the deaths have not been included in the official Covid-19 death toll if they are related to the pandemic - or what the other cause might be if they are not.
The localised analysis comes as the latest weekly figures released on Tuesday by the ONS show that the number of Covid-19 deaths in all settings in England and Wales had reached 44,401 by May 22.
The ONS figures, released at later points than the daily Department of Health numbers, have been consistently higher than previously recorded as the Department of Health was initially only recording deaths among hospital patients who had tested positive and were reported up to 5pm the day before.
The ONS provides figures based on all deaths registered involving Covid-19 according to death certification, whether in or out of hospital, for England and Wales.
Adding the latest ONS numbers for England and Wales to more recent figures from the NHS and from authorities in Scotland and Northern Ireland means the UK death toll has now officially topped 50,000.
It comes as new figures show that the north of England has nearly twice as many new infections of coronavirus than London, making it the new epicentre of the crisis in the UK.
Cases in the North East and Yorkshire and the North West have soared as numbers in the capital drop, according to figures from the Covid Symptom Study.
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It estimates that 173,879 people currently have symptomatic Covid-19 in the UK.
In the past week, Hull has been identified as having one of the worst infection rates in Yorkshire.