Virgin Trains said the service was held up outside Euston for 47 minutes under the pretence that there were signalling difficulties.
But the smoke-screen allowed officers to assemble and meant the two men were not aware of their impending arrest.
A Virgin Trains spokesman said when the train pulled into the busy station passengers were allowed off, but the whole area was surrounded by police.
The two men were arrested without a struggle by officers from British Transport Police and the train was sealed for two hours while it was checked for evidence.
"Passengers were told there was a problem with signalling equipment and we weren't sure how long it would take to sort out," the spokesman said.
"People at the time were quite unhappy they were sitting so close to the station. But it provided a smoke screen so the two people wouldn't know what was happening."
They were later transferred to Birmingham where they were today being quizzed at Queen's Road police station.
