A "suspicious package" was found aboard a South West Trains (SWT) service on Thursday evening.
Officers from British Transport Police (BTP) were called to Winchfield railway station at around 6.20pm after the item was reported to police by a member of rail staff.
The train was travelling between Farnborough and Basingstoke.
It came to a halt at Winchfield where officers boarded to investigate.
The package was later declared "unsuspicious".
A spokesman for BTP said: "We were called to Winchfield railway station just before 6.20pm.
"There were reports of a suspicious package, which was reported to us by a member of rail staff.
"It was quickly deemed unsuspicious and lines re-opened shortly after."
Passengers were warned of possible delays, cancellations and alterations on Basingstoke-bound trains. SWT later confirmed all lines had reopened by 7.15pm.
A spokesman for SWT said police were "carrying out investigations on a train" and apologised for delays caused.
The operator added on Friday morning it could not comment further as the incident was a police matter.