PRESS ASSOCIATION --The hunt continued today for a potential saboteur after packs of Nurofen Plus were found to mistakenly contain anti-psychotic and anti-epileptic drugs.
Reckitt Benckiser, the drug's manufacturer, recalled the product last night and halted distribution after discovering five boxes contained other companies' medicines.
It has estimated some 250,000 packets are still in customers' hands.
Scotland Yard launched a probe after four boxes were found to contain the anti-psychotic drug Seroquel XL 50mg and one packet contained Pfizer's anti-epileptic medication, Neurontin, in 100mg capsules.
Its Specialist Crime Directorate (SCD), which tackles serious and organised crime, is now investigating.
Examinations will cover the entire production chain in a bid to identify how some packs of Nurofen Plus came to contain strips of the potentially harmful drugs after Thursday's safety alert.
Dr Aomesh Bhatt, medical director for Nurofen Plus, said: "We are taking this matter extremely seriously and have decided to recall all packs of Nurofen Plus as the most prudent course of action in the current circumstances.
"We're asking consumers to return any packs of Nurofen Plus to a pharmacy. No other Nurofen products are affected or being recalled."
Ian Holloway, of the Medicines and Healthcare products Regulatory Agency's Defective Medicines Report Centre (DMRC), said: "People should check to see if they have any packets of Nurofen Plus.
"If you do, return them to your nearest pharmacy."
Seroquel XL is a prescription-only anti-psychotic drug used to treat several disorders including schizophrenia, mania and bipolar depression.
People who accidentally take the drug may experience sleepiness and are advised not to drive or operate any tools or machinery until they know how the tablets have affected them.
Professor David Nutt, head of the department of neuropsychopharmacology and molecular imaging at Imperial College, said: "The effect of taking Seroquel entirely depends on the dose.
"The only likely impact of a single ingestion would be sedation, but in people taking antihistamines and other sedatives the added effects could be quite extreme."
Neurontin, used to treat epilepsy and long lasting pain caused by damage to the nerves, can also result in drowsiness and lack of co-ordination.
Common side-effects of the prescription-only drugs, which may be seen in more than one person in 100, include pneumonia, depression, loss of vision, breathing difficulties and nausea.
A Pfizer spokesman said: "We advise any person that may have taken this medicine by mistake to seek medical advice and return the pack and contents to the nearest pharmacy."
Nurofen Plus is for pain relief and contains codeine. The affected packs all contain 32 tablets.
The large capsules of Seroquel XL 50mg tablets have gold and black packaging while Neurontin, which comes in a two-piece, white capsule, is stored in white and silver blister packs.
Nurofen Plus capsules have silver and black packaging.