The 57-year-old local man was initially arrested on suspicion of attempted murder but has now been detained for 28 days under Section 2 of the act for an assessment of his mental health.
Police enquiries into the incident – which is not being treated as a terrorism incident – are continuing.
Police called at about 9.30am yesterday (Wednesday, Dec 2nd) to a report of a stabbing inside the Marks and Spencer store on St James Street in the town.
Two women – a member of shop staff in her 40s and a member of the public in her 60s – received stab injuries and were taken to hospital for treatment. One has now been discharged and the other remains in hospital.
The attacker was detained by members of the public and store staff. A knife was recovered.
The store was closed yesterday but has re-opened this morning. There will continue to be extra high visibility police patrols in the town centre to offer reassurance to businesses and shoppers.
Supt Stasia Osiowy, of East Police, said: “Our enquiries into this incident are ongoing and I would like to continue to appeal to members of the public who may have seen or filmed this incident, or who have information which could assist, to get in touch with us.
“Mercifully while the injuries caused in this incident were serious, they are not life threatening and the two women involved are continuing to receive the support of specially trained police officers.
“I would like to stress again this is not being treated as a terrorism incident and we continue to keep an open mind as to motivation of this individual.
“I would like to thank the community for their understanding and co-operation while we dealt with an incident which clearly had the potential to cause a great deal of concern.
“We will continue to update people on the course of our investigation as and when we can and there will continue to be extra patrols in the town centre to reassure. If anyone has information or concerns then please do speak to an officer.
Anyone with information should contact police on 101 quoting log 0313 of December 2nd or independent charity Crimestoppers on 0800 555 111.