Police are investigating after around 8,000 bluebell bulbs were found dug up from a privately-owned wood and loaded into large sacks and mail bags.
Officers discovered the recently-uprooted bulbs after a member of the public reported people acting suspiciously at the wood in the Fakenham area on March 23, Norfolk Police said.
The force said two men aged in their 30s and two women aged in their 20s, all from Lincolnshire, were interviewed, but that no arrests have been made.
The landowner is now in the process of replanting the bulbs, and officers are appealing for witnesses.
British Bluebells are protected under the Wildlife and Countryside Act along with all other native wild plants and bulbs, the force said.
This means it is an offence to intentionally uproot any wild plant unless authorised to do so, and police are encouraging people to report any suspicious behaviour.
In 2019, almost 13,000 snowdrops worth about £1,500 were stolen from the Walsingham Estate in Norfolk.
Walsingham has been a place of pilgrimage since the Middle Ages and styles itself as “England’s Nazareth”.
Two men admitted theft and criminal damage over the incident, with one sentenced at Norwich Crown Court in 2019 to 10 months in prison and the other ordered to complete 200 hours of unpaid work.