Three people who were hospitalised with suspected carbon monoxide poisoning after a gas leak school in Stevenage today are "not in a serious condition".

Police, fire and ambulance crews were called to Martins Wood Primary School in Mildmay Road just after 1pm, following reports of a number of children and adults becoming unwell.

One adult and two children have been taken to Lister Hospital by ambulance with suspected carbon monoxide poisoning, while a further six adults and nine children were assessed at the scene.

In an update, Zoe Phillips, executive headteacher at Martins Wood Primary School, confirmed that the three people hospitalised are "not in a serious condition".

"Just after midday, a member of staff became ill. Shortly after this, two pupils also started feeling unwell," she said. 

"The emergency services were called and the school was evacuated. Pupils were safely escorted out of school by staff while the building was investigated by Hertfordshire Fire and Rescue for a possible carbon monoxide leak.

"The staff and two pupils were taken to Lister Hospital for monitoring. They are recovering well and their condition is not serious."

The gas leak is believed to be an isolated one, with Hertfordshire Fire and Rescue carrying out an investigation.

Ms Phillips also confirmed that the school would remain closed tomorrow (June 13), but is expected to reopen on Friday.

"The school will remain closed tomorrow for further safety checks and we hope to reopen on Friday," she said.

"We will keep parents updated on this via email and social media. If your child starts feeling unwell, or you have any concerns about their condition, please call NHS 111 who will be able to advise you."