Cannabis plants with an estimated street value of €400,000 were discovered in an abandoned van in Co Meath on Saturday morning.
In excess of 500 plants were found by gardaí in the van on the M3 motorway near Dunshaughlin shortly before 9am.
No arrests have been made to date and Garda enquires are ongoing. The van has since been removed for technical and forensic examinations.
Gardaí said the cannabis plants have an estimated street value of €400,000, pending analysis.
They are appealing to anyone who witnessed any suspicious activity on this stretch of motorway overnight to come forward. They are particularly appealing to motorists who may travelled along the route to review any dash-cam footage recorded and make it available to investigators.