Investigators in the Senate say that China has hacked into "computers belonging to Pentagon contractors" nearly two dozen times.

A yearlong investigation announced Wednesday by the Senate Armed Services Committee identified at least 50 intrusions since 2012 against unspecified contractors working for the U.S. Transportation Command, or Transcom. It said at least 20 break-ins were highly sophisticated and blamed those on China's government.

The Senate report, which was recently declassified, says that the contractors had "failed" to report the hacks to the Pentagon, despite their contractual obligation to report them.