Acting U.S. Defense Secretary Patrick Shanahan has reportedly provided his Chinese counterpart with visual evidence that North Korea has violated international sanctions in waters near the Chinese coast.

The Associated Press(AP) reported on Tuesday that Shanahan delivered the material in a meeting with China’s Defense Minister Wei Fenghe on the sidelines of the Shangri-La Dialogue in Singapore June first.

Compiled into what the U.S. defense chief described as a “beautiful book,” 32 pages with a series of photographs and satellite images were presented to Wei along with dates, times, and other descriptive information.

The AP says the photos show North Korea engaged in illegal oil shipments near China’s coast, breaching international sanctions.

A Pentagon official was quoted as saying that the Chinese minister was surprised when he received it and immediately handed it over to a staff officer at his side. 

The AP said presenting evidence of North Korean sanctions busting near China’s borders was Shanahan's idea, and was intended to demonstrate the potential for coordination and collaboration with Beijing regarding sanctions enforcement.