During the afternoon, officers were called to a report of a man taken ill near to Merkland Recreation Centre in Hillhead, Kirkintilloch, and it has been established that he took tablets he found lying nearby.
He was taken to hospital where hospital staff describe his condition as serious but stable.
Officers attended the area and found the bag of blue coloured round tablets yesterday evening. They are currently undergoing analysis.
Enquiries are continuing and police are asking the public to get in touch if they have any information.
Sergeant Saul Gadsden of Kirkintilloch Police Office said: “We are carrying out enquiries into how this bag of tablets was left lying in a public place and how long it was lying there for.
“If ingested, these tablets could cause considerable harm, especially to children.
“There is no safe way to take drugs and at this time I would urge anyone who may have picked up any of these tablets, not to take them, or if anyone has taken them, then please seek medical advice.
“Although our enquiries are at an early stage, anyone with information that will assist us should contact Kirkintilloch Police Office through 101.”