Missionary Veronica "Roni" Bowers, 35, and her 7-month-old daughter Charity, of Muskegon, were killed April 20 when the Peruvian Air Force fighter jet opened fire on their single-engine Cessna after mistaking it for a drug-smuggling flight.
Her husband Jim Bowers, 38, and their 6-year-old son, Cory, survived unhurt.
Pilot Kevin Donaldson was seriously wounded when the plane was shot down.
Citing several unnamed sources familiar with the report, the paper said it does not assign direct blame to either country for the April incident in which the plane was shot down over northern Peru.
The small private plane was tracked by a CIA surveillance plane flown by American contract employees who relayed information to the Peruvian Air Force.
The Post said that although its sources declined to provide specific details of the report, they said it characterizes the U.S.-Peru drug interdiction program as having limited U.S. oversight and having evolved over the years into lax adherence by both countries to established procedures.
Top department officials traveling abroad with Secretary of State Colin Powell said they were unfamiliar with contents of the report.
The Post, which cited sources as saying a Senate Select Committee on Intelligence as reaching similar conclusions, said the administration inquiry has been withheld while officials try to figure out what to do about the program.
It quoted an administration officials as saying a "collective" decision was made in June by "the most senior levels of this government" to withhold the report, pending a separate policy review.
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