Emergency services were called to the warehouse on Cloch Road at Faulds Park in Gourock, Inverclyde, following the alert at 5.15am on Friday, STV reported.
Hundreds of staff are understood to have been evacuated from the depot.
A Police Scotland spokeswoman said: “At around 5.15am, police received a report of a suspicious package found at a depot in Gourock.
“Emergency services are in attendance and the premises have been evacuated as a precaution.
“The item will be examined and enquiries are ongoing.”