Two jeeps were abandoned after getting stuck in the mud during illegal off-roading on moorland.
The National Trust says the incident has been reported to the police.
The 4x4s were discovered this weekend on the Standedge Trail, a bridleway across Marsden Moor in the hills above Oldham.
In a statement on Facebook, the National Trust said the moor is a 'protected site, home to rare species and precious blanket bog'.
The statement said: "These vehicles have been abandoned on Marsden Moor after becoming stuck this weekend.
"They were driving along Standedge Trail. This is a bridle path, which is not for vehicles.
"Off-roading on Marsden Moor is illegal.
"This is a protected site, home to rare species and precious blanket bog.
"This incident has been reported to police.
"We have increased our weekend ranger patrols, but can't be everywhere at once.
"Please keep reporting illegal off-roaders on Marsden Moor to the police. We are also in the process of having signs installed on this route."
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