It has been reported that eight prisoners at Highpoint Jail in Suffolk fell ill after getting into an unlocked medicine cabinet.
The Prison Service has confirmed it has launched an investigation into the incident.
It says all the prisoners who required medical treatment were taken to hospital and returned to the prison at Stradishall the next day and that action will be taken against those involved.
The Ministry of Justice has confirmed that a wing at Chelmsford prison is being re-opened.
Some older parts of the jail were closed last year.
Figures for February show the jail was almost at its capacity.
The move to reopen a wing is being described as a sensible response to ensure there are enough prison places for those sentenced by the courts.
Nine prisons in the Anglia region have been named as part of a network of resettlement jails that have been been unveiled by the Justice Secretary Chris Grayling as part of a shake-up of the prison estate.
The introduction of 70 resettlement prisons across England and Wales will see the majority of offenders released from prisons in, or close to, the area in which they will live.
Existing prisons up and down the country will function as resettlement prisons with a trial starting in the north west of England in the autumn.
The prisons in the Anglia region are: Peterborough, Norwich, Wayland near Watton in Norfolk, Hollesley Bay in Suffolk, Highpoint near Bury St Edmunds, Chelmsford, The Mount in Hertfordshire and Woodhill in Milton Keynes.
A new report says privately owned prisons, like the one at Peterborough, are better run, with lower offending rates among inmates.
The report is by the right leaning think tank Reform. Jonathan Wills spoke to its author, Will Tanner, who began by running through the reasons why he thinks private is better than state when it comes to prisons.
Six prisons in England, which together can hold up to 2,600 prisoners, are to close, the Ministry of Justice said today.