A winning bid could be announced within two weeks, one source said, though another source said the process had stalled several times over the past few months and could yet falter. The Stamford, Conn.-based company, which has about $50 million in Ebitda, hired Citibank NA to run an auction this summer.

James Berger, now 85, founded World Courier in 1969 and is the majority shareholder. No institutional investors own any equity in the company, but members of management do, one source said. World Courier gives its employees generous bonuses and compensation packages, the source said.

The auction, which commenced in the summer, drew considerable interest from both PE firms and large logistics companies, but it didn't exactly sail through the process. Second-round bids were due in August; then all was silent for weeks.

One source suggested the company may have been concerned with preserving the employee benefits structure.

"It's been a very strange and unusual process," the source said.

Management presentations went ahead in November, but then the auction was put on hold until January, sources said.

World Courier also had some difficulties in providing documentation to potential buyers.

Private equity has some history in World Courier's niche sector. Its primary competitor, Marken Ltd., was acquired by U.K. buyout shop Apax Partners Worldwide LLP in December 2009 for £975 million ($1.6 billion) in an all-equity transaction. Apax trumped a rival offer from Hellman & Friedman LLC said to be around £800 million at least initially. Apax later tapped a financing package to leverage its equity.

However, that investment may not have fared as well as expected. Earlier this month, the London-based pharmaceutical logistics provider hired Houlihan Lokey Inc. to advise on a company restructuring, one source said.

The source suggested that Centerbridge may be interested in buying Marken's debt and then possibly combining the company with World Courier later.

The source indicated that World Courier may be better positioned than Marken, which transports test samples, rather than drugs, from clinical sites to laboratories for analysis. Marken has more competition in this business segment because regulations tend to be less onerous.

Marken, with only three major clients, appears to have suffered from the loss of one of its biggest, the source added.

In comparison, the source said, World Courier has a more diverse client base comprising biopharmaceutical companies, contract research organizations, clinical trial suppliers and laboratories.

GTCR, World Courier and Citi declined comment. Apax, Marken, Centerbridge and Houlihan Lokey did not respond to requests for comment.