UPS drivers are making deliveries in U-Haul trucks - and people are panicking and calling the police

UPS is renting out hundreds of U-Haul trucks across the county as it faces mounting pressure to deliver packages on time ahead of Christmas.

The trucks are a "cost-effective way to expand our delivery fleet," UPS spokesman Brian Hughes told Business Insider.

He said it's common for UPS to rent additional trucks during the holidays.

The UPS-driven U-Haul trucks have been spotted rolling through neighborhoods across the country, and in some cases they have caused some alarm.

Edward Jones analyst Brian Yarbrough told Business Insider that he was a little concerned when he saw a U-Haul truck park outside his house recently. He said he kept an eye on the driver as he emerged from the truck and pulled a package out of the back, before realizing he was a UPS worker.

In Louisville, Kentucky, some people started calling 911 after spotting U-Haul trucks near their homes, WDRB.com reports.

Residents said they were worried that criminals could be dressing as UPS drivers to fool them into opening their doors.

Concern escalated when rumors circulated online claiming terrorists were using UPS uniforms to deliver bombs, according to WDRB.

UPS is expanding its truck fleet as it faces an unexpected surge in online purchases this year that's resulting in some shipping delays.

"We're seeing it first-hand all over the place, at least in the New York area, that there are at least slight shipping delays," Nasdaq analyst Jonathan Eyl told Business Insider.

Many customers are complaining about delayed shipments on social media.

"My packages have been sitting sitting six miles away for nine days," one customer wrote on UPS's Facebook page.

Another customer wrote: "They lied that my package was on the truck and would be delivered every day this week by 7 p.m. Come to find out it never went at all. Now it's the weekend and I still don't have package and they closed."

UPS has been responding to nearly every customer complaint on Facebook by asking them to email their tracking numbers so the company can investigate.

The company hired up to 95,000 extra workers this season to help manage the holiday rush, in addition to renting additional trucks.