PRESS ASSOCIATION -- he makers of Nurofen Plus have recalled the tablets and confirmed sabotage is suspected in packets of the painkillers.
Five reported cases of other manufacturers' medicines were discovered in boxes of Nurofen Plus, with a spokesman for manufacturer Reckitt Benckiser (UK) Ltd saying: "Sabotage is suspected and we are working with the police on a formal investigation to find the person or persons responsible. Distribution of Nurofen Plus has been halted at this time."
Dr Aomesh Bhatt, medical director for Nurofen Plus, added: "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."
Investigators began trying to establish how some packs of Nurofen Plus came to contain strips of a potentially harmful anti-psychotic drug after Thursday's safety alert.
Consumers were warned to check their supplies after the Medicines and Healthcare products Regulatory Agency (MHRA) issued a warning that some packs contained Seroquel XL 50mg.
Three packs of Nurofen Plus were found to contain blister packs of the anti-psychotic medicine. They were bought in Victoria, Bromley and Beckenham, south London. In each pack, the end two capsules of Seroquel XL had been cut off.
But on Friday, two more packets were found. One contained Seroquel XL 50mg tablets and the other contained the Pfizer product Neurontin 100mg capsules.
The Reckitt Benckiser spokesman added: "The safety of our consumers is paramount. Even though there have been no serious health consequences to any consumer, we will not take any risk regarding the quality or safety of our products. This decision has been taken in full consultation with the Medicines and Healthcare products Regulatory Agency as a precautionary measure."
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."