Investing.com -- Shares of several trucking companies fell sharply on Tuesday after Amazon announced the U.S. expansion of its less-than-truckload freight service to any destination and any business size, rattling investors in the transportation and logistics sector.

Old Dominion Freight Line dropped 7.3%, FedEx Freight fell 5.2%, Knight-Swift slid 5.4%, and Saia moved 8.2% lower following the announcement.

Amazon is expanding its less-than-truckload service, which allows businesses to share trailer space for partial loads rather than reserving a full truckload, beyond its existing inbound-to-Amazon offering to include third-party warehouses, distribution centers, and retail partners.

The service, which has operated since 2019 and moved millions of pallets last year, is now open to businesses of all sizes shipping typically between one and six pallets.

The expanded offering is part of Amazon Supply Chain Services, a logistics portfolio backed by more than 80,000 trailers and 24,000 intermodal containers. Amazon is also offering next-day live pickup, same-day drop trailer pickup, real-time GPS tracking, and cargo camera monitoring as part of the service.

"Now Amazon LTL can move your freight wherever it needs to go, servicing destinations nationwide for businesses of all sizes," said Jim Ruiz, director of Amazon Freight.

The announcement adds to investor concern that Amazon's growing logistics ambitions pose a structural threat to freight carriers.