The Narcotics Control Board (NACOB) has intercepted 5,851 compressed slabs of cannabis in an operation at the Tema port.
The seizure, one of the biggest narcotics busts in the history of the country, has an estimated street value of £29.2 million.
The drugs were concealed in boxes of yam set for export to the United Kingdom.
Checks by NACOB revealed that the cannabis was compressed in yellow cellophane underneath all the boxes.
Two suspects have so far been arrested in connection with the bust, while a third one is on the run.
The suspects, Dominic Kojo Amenyo and Osae Akotua are both freight forwarders at the Tema port and were handling the yams.
A third suspect, one Bright, also a freight forwarder, is said to be on the run, according to a report in the Daily Graphic.
The Executive Secretary of NACOB, Francis Torkornoo told the paper that his outfit had been cooperating with the Ghana Revenue Authority and Police at the Tema port.
Security agencies first became suspicious on March 7 when the yams were in storage for customs checks before export.
Dominic Kojo Amenyo claimed to police he was on his normal rounds when Osae Akotua called him to assist with the yam.
Amenyo told police he did not know the actual exporters or owners of the boxes containing the yam.
It was Osae Akotua who fingered the third suspect, Bright. He said bright had asked him to handle the processing of the documents for him.