Portland police are investigating a break-in at the Rite-Aid pharmacy at 701 Forest Ave. that yielded a number of prescriptions that had been filled for customers.

Police and a store representative responded to a burglar alarm at the pharmacy just before midnight Monday but found the building secure, said Lt. Scott Pelletier, head of detectives for the department. Officers checked on it an hour later and saw nothing amiss.

Investigators are trying to determine whether the alarm reset after the initial alert.

Police received a call from a resident on Codman Street nearby about trash in the form of empty pill bottles in their yard and paper bags with the Forest Avenue pharmacy’s name and address attached. Officers returned to the pharmacy and found that the drive-through window had been broken out.

The person who broke in stole prescriptions that had been filled for customers to pick up but the locked cabinets where the narcotics and other commonly-diverted medications are kept was not broken into.

The pharmacy is still conducting an inventory to determine what was taken. Police ask that anyone who saw anything suspicious in the area between about 1 a.m. and 6 a.m. call the detective bureau at 874-8533.

Police are viewing security video to obtain images that might help identify the burglar.