Police and national park officials are investigating after a 4x4 vehicle has been left near the summit of Snowdon again.
It comes less than a month after a similar incident with the same vehicle. It is not known who drove the Vauxhall Frontera up the mountain this time.
Snowdonia Mountain Railway staff arrived to find it parked near the summit visitors centre.
North Wales Police said nobody had been arrested.
National park officials condemned what had happened as "irresponsible".
Alan Kendall, general manager of the railway said: "After we found the vehicle this morning, we checked the point mechanism on the line to ensure that no damage had been caused overnight. Our trains are running.
"We have a very busy weekend ahead of us and this vehicle will not be moved until next week at the earliest.
"To move the vehicle sooner would mean suspending trains and spoiling visitors' plans. We won't be doing that."
North Wales Police were told earlier on Thursday that a vehicle was parked near the summit building and their inquiries are underway.
Snowdonia National Park Authority officials are also investigating.
Authority chief executive Aneurin Phillips said: "This irresponsible behaviour is totally unacceptable and I urge the police to prosecute the offender and impound and dispose of the vehicle."
The authority said in a statement it was deeply disappointed by the "irresponsible act that has again posed unnecessary danger and risk to both mountain users, the landscape and Hafod Eryri [visitor centre] itself".
The park authority said it has been in contact with police, mountain rescue teams and the mountain railway to immobilise the vehicle "in the interest of public safety and to prevent damage to our property".
The same 4x4 was found abandoned on 3 September but 365m (400 yards) below the summit.
It was eventually taken down by the mountain railway on a trailer.
A BBC reporter, who travelled to the summit on Thursday, said the vehicle matched the description and number plate of the vehicle from the earlier incident.
It has not been confirmed who drove the vehicle up the mountain on this occasion.
A man has been charged with dangerous driving offences in relation to the earlier incident and is due before magistrates on 7 October.