An annual report to Congress touched off a round of speculation Wednesday about the motives of a small Chinese Internet service provider that briefly rerouted as much as 15 percent of the world’s Web traffic on two occasions last spring.

The report, by the United States-China Economic and Security Review Commission, noted that the service provider, IDC China Telecommunication, broadcast inaccurate Web traffic routes for about 18 minutes on April 8. That information was then retransmitted by China’s state-owned China Telecommunications, effectively forcing data from the United States and other countries to pass through Chinese computer servers. A similar episode in March drew less attention.

The report said the move affected data traveling over both the government and military networks of the United States, including information from the Senate, the Army, the Navy, the Marine Corps, the Air Force, the secretary of defense’s office, NASA, the Department of Commerce and the National Oceanic and Atmospheric Administration, as well as from many American companies.

The incidents, which were widely reported when they occurred, were never explained, although Chinese engineering managers said that the routing errors were accidental.