Thousands of public defibrillators could be useless due to an electrical fault.
This fault means devices in Cedars Youth & Community Centre in Chicheley Road, in Rooks Heath College or in schools might not work.
The manufacturer Physio-Control has issued a safety alert to people and organisations with the defibrillators, including instructions on what to do.
John Wilkinson, MHRA's director of medical devices, said: "These devices deliver life-saving treatment and it is vital that they work in an emergency.
"Those responsible for them should carry out the instructions by the manufacturer.
"If you have any questions, or have not got the manufacturer's safety alert, call Physio-Control's customer support on 0808 258 0094."
There have been no reports of failures when treating patients but the MHRA urged owners to check the serial number on their device matches that on the confirmation sheet received from the manufacturer, or the alert on its website.
Owners can tell if their defibrillators are faulty if a voice prompt fails to initiate within five seconds.
In those instances the MHRA recommended removing the device and calling the manufacturer.
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