More than £100,000 worth of drugs has been seized at Norwich Prison over the past eight months as part of a crackdown on smuggling.
Prison governor James Shanley said people had thrown tennis balls, oranges and dead pigeons, which were filled with drugs, over the jail's fence.
Sniffer dogs had been used to sweep the jail's grounds and find the drugs.
Figures show eight out of 10 inmates at the Norfolk jail were imprisoned for drug or alcohol-related crime.
Last week an inspectorate report described the jail's overall performance as poor.