London (CNN) -- A common over-the-counter painkiller has been recalled across Britain amid sabotage fears, health authorities said.
The recall came after five reported instances of rogue tablets were found in packets of Nurofen Plus, a nonprescription painkiller that contains codeine.
Police are now investigating the "suspected sabotage," according to Reckitt Benckiser, the makers of Nurofen Plus.
The Medicines and Healthcare Products Regulatory Agency issued a safety alert Thursday when three packages of Nurofen Plus were found to contain strips of an antipsychotic drug, Seroquel XL.
Reckitt Benckiser moved to a full recall -- which could involve 250,000 packets of Nurofen Plus -- late Friday after two more packages were found to hold rogue strips of prescription-only drugs.
One contained Seroquel XL and the other Neurontin, a medicine made by Pfizer that's used to treat epilepsy pain caused by nerve damage.
The Seroquel XL 50mg tablets, manufactured by AstraZeneca, are used to treat such illnesses as schizophrenia, mania and bipolar depression.
"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," Reckitt Benckiser said in a statement.
Only two people are known to have taken the wrong drugs, a spokeswoman for Reckitt Benckiser confirmed to CNN. Both took Seroquel XL and are reported to be well.
"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," Dr Aomesh Bhatt, medical director for Nurofen Plus, said in a company statement.
The regulatory agency has urged people to return any packets of Nurofen Plus to their nearest pharmacy. A refund will be given, Reckitt Benckiser said, adding that no other Nurofen products are affected.
Anyone who has taken a tablet and has questions should consult their physician, the drug regulatory body said in a statement.
Common side effects of Seroquel XL include dizziness, headaches and weight gain, a spokesman for the agency said.
Neurontin can cause dizziness if taken by healthy people, Reckitt Benckiser said. No one is thought to have taken it in error.
Manufacturing of Nurofen Plus has been halted while the recall of stock from consumers and parmacies is carried out.
CNN's Laura Smith-Spark contributed to this report.