At around 1.40am this morning, Tuesday, British Transport Police (BTP) were called to reports of two people gaining access to the train at Lockerbie, Dumfries, and Galloway.
The Warrington Guardian understands the destination of the train was Warrington Royal Mail.
The two young men, who have now been confirmed as teenagers, were said to have damaged signalling equipment in the process.
Officers have said nothing is thought to have been stolen but a number of parcels appear to have been ‘interfered’ with.
A BTP spokesperson said: “Officers attended and a 17-year-old and an 18-year-old were located in a carriage and arrested.
“At this stage it’s not believed anything was stolen but a number of parcels in the carriage had been interfered with.
“Both young men have been charged with malicious mischief, theft and threatening and abusive behaviour.”
The force said inquiries are ongoing and anyone with information about the incident should contact them by texting 61016 or calling 0800 40 50 40, quoting reference 38 of August 1.