APX Logistics, the country's largest parcel consolidator, ceased operations on Thursday and the United States Postal Service was moving to take on large numbers of shipments caught in transit.

Officials at APX, a California-based provider that claims $700 million in annual revenue, gave no reason for the shutdown. One senior executive said majority owner Heritage Partners had decided the business should file for Chapter 11 bankruptcy protection.

Calls to Heritage, a private equity firm in Boston, were not immediately returned. Heritage formed APX in 2004 when it acquired the small package division of RR Donnelley Logistics and combined it with American Package Express.

The USPS was trying to confirm the status of one of the country's largest business to consumer package consolidators "but indications we've received is that they've folded," said USPS spokesman Gerald McKiernan.

McKiernan said the USPS is trying to arrange alternative providers but "in the meantime, the postal processing network will fill in the gaps."

APX says it handles about 250 million packages annually through the U.S. Postal Service - more than any other carrier with USPS - and operates more than 400 trucks out of 47 facilities nationwide that manage more than 200,000 truckloads a year.

John D. Boyd