Consolidate stacking as much as you possibly can........you may want to rent a trailer for temporary storage so you know product that is arriving now isn't getting contaminated. Move as much stuff out as you can and delay shipments in if possible
Mice are very smart.........and if employees have seen 2 in the middle of the floor and not up against a wall then you've got a lot of mice in there.
Any pallets that are securely wrapped should be carefully inspected then unwrapped and wrapped again; then put those in the trailer. Do not put any skids directly onto the warehouse floor until this is corrected.
Given that this is the dead of winter, these critters found a way in in the fall and have been happily breeding since then. If you're in a part of the states that is frozen now, you won't get anymore moving in (yeah for that) so you need your PCO to find the buggers..........that means they need to come either really early or really late when the facility is at it's quietest.
This may help too
https://www.qualitya...ood-case-study/ it's about a warehouse mouse infestation and how it was handled
I agree with the contributors, but I know that Scampi's suggestion works. Unfortunately, this means a lot of inspection, but it is truly worth it in the end. If you go with this option, you will want to make sure that you use docks furthest away from the known sightings, so that you don't end up with an unwanted visitor inside your checked product in the trailer. When you are taking breaks or are done for the day, make sure that you lock and seal the trailer and pull it away from the building to minimize any risk of your little critters getting in the trailer as well. I would suggest maybe 2 or 3 trailers so you can have them on rotation. You could be putting the inspected product on one trailer and possibly unloading and loading for shipment with another (if you have the luxury of multiple docks away from your problem area).
You should have basically three sectors of process - the product in which you suspect might have come in contact with the mice, a separate area for the product you are actively checking, and then the load out points for the product. Be sure to place extra traps around the area where you are inspecting product in the event you find something interesting (particularly wall borders and doorways).
As suggested, you should have a blacklight and a flashlight handy for this task.
As previously mentioned, you should definitely walk through the warehouse and look for any possible openings, and contact your PCO to have them come out on a very frequent basis until you have this under control (on order of 2-3 times a week). They should be able to look around and find any potential areas that may have harborage as well.
May the force be with you.