Two people are being questioned at Longford garda station in connection with what has been described as a vicious robbery in the town on Wednesday night.
It happened at a private car park near the train station at around 9.30pm when a woman who had travelled from Dublin was walking to her car.
She was approached by a number of people who demanded she hand over her bag and other possessions, while a young man who came to her assistance was assaulted.
Gardaí believe the woman may have been targeted on the train and followed when she got off in Longford.
Superintendent Jim Delaney told Shannonside FM their investigation has progressed quickly.
"We conducted some searches this morning with the assistance of the western regional armed support unit," he said.
"We do have a male and female in custody, detained in connection with the investigation.
We are still anxious to appeal to anybody that was on the train or anybody that was in and around the area of the Longford train station at 9.20pm or thereafter.