FILE PHOTO - A United Parcel Service (UPS) truck on delivery is pictured in downtown Los Angeles, California October 29, 2014. REUTERS/Mike Blake

(Reuters) - United Parcel Service said on Tuesday some deliveries were being delayed because of a surge in holiday online shopping orders during the peak shipping period.

Atlanta-based UPS, which has made major investments to upgrade and expand its facilities, said it shifted more employees and other resources to certain markets in its network and expected to have the issue resolved by midweek.

“As a result of unprecedented shipping volumes in certain markets during cyber week, UPS has added one- or two-day time-in-transit on some deliveries,” the company said in a statement.

The world’s largest package delivery company has been preparing all year for the crucial peak shipping period. It also unveiled a number of surcharges in recent years, seen as a way to manage the higher costs associated with e-commerce and unwieldy packages.

UPS said the vast majority of the 750 million packages it delivers during the holiday season “will be delivered in accordance with the service commitments for the specified time-in-transit.”

“This year’s forecasted volume is about 5 percent more than 2016’s holiday volume of more than 712 million packages. That’s about 40 million more packages than last year,” UPS said.