A suspicious package that triggered a security alert in Victoria's north-west was two pairs of underpants in a suitcase, police say.

Police said a member of the public reported a black suitcase placed outside a shopping centre carpark in Mildura about 7:30pm (AEDT) on Sunday.

The shopping centre and the immediate area were evacuated and the bomb squad was called in from Melbourne, more than 500 kilometres away.

Inspector Simon Clemence said the threat was cleared after the suitcase turned out to contain underwear.

"It turned out to be two pairs of underpants and we would very much like to find the person that fits those underpants," Inspector Clemence said.

"We didn't even need to detonate the underwear so that's excellent.

"I'm sure it was just accidental but if we do see someone running around without any underwear on we'll have a chat with them."

The area was in lockdown for about 10 hours before the threat was cleared.

Inspector Clemence said the bomb squad had to drive about six hours from Melbourne to Mildura.

"Unfortunately because we're so far away it was about four o'clock in the morning before the bomb squad could arrive from Melbourne," he said.

"They have a massive amount of equipment with them and it took that long before we could actually clear the area and let people go back in."

He said it was fortunate that there were not many people in the city at the time.

"But it tied up all our police resources for most of the night," he said.

Police are yet to find the owner of the underpants.