New Delhi, Aug. 29 -- When President Donald Trump's administration last month awarded a contract worth up to $1.2 billion to build and operate what it says will become the nation's largest immigration detention complex, it didn't turn to a large government contractor or even a firm that specializes in private prisons.

Instead, it handed the project on a military base to Acquisition Logistics LLC, a small business that has no listed experience running a correction facility and had never won a federal contract worth more than $16 million. The company also lacks a functioning website and lists as its address a modest home in suburban Virginia owned by a 77-year-old retired Navy flight officer.

The mystery over the award only deepened last ...