The company has been accused by environmentalists of regularly buying from a Chinese supplier that traffics in illegally harvested Russian oak. Lumber Liquidators disputes the claims, saying that it carefully monitors the origins of its wood.

Here in Pucallpa, a city at the heart of Peru’s logging industry on a major tributary of the Amazon, the waterfront is dominated by huge sawmills piled high with thousands of massive logs. They are floated in from remote logging camps, pulled by small motorboats called peke pekes, while trucks stacked with logs and lumber jam the roads.

A military officer stationed here to patrol the Ucayali River said that he had largely stopped making checks of the riverborne loads of timber, though the checks are supposed to be mandatory. In the past, he said, he had repeatedly ordered loads of logs to be held because they lacked the required paperwork, only to learn that forestry officials would later release them, apparently after creating or rubber-stamping false documentation.

In some cases, he said, loads of mahogany, a valuable type of wood that has disappeared from all but the most remote areas, were given fake documentation identifying the wood as a different kind.

“It’s uncontrollable,” said the officer, who was not authorized to speak publicly. Referring to local forestry officials, he said, “The bosses give jobs to people they trust and then take a cut of the bribes they get.”

Mr. Berrospi, who worked as an environmental prosecutor until August, recited a bitter catalog of frustrations. The local authorities are paid off by loggers to create or approve false paperwork, he said. On one occasion, he said, he was offered about $5,000 to stop an investigation. He reported it to a local prosecutor who specialized in corruption cases, but said he was dismayed by the response.