The National Police Agency issued an advisory to all prefectural police forces in December to avoid questioning people in a way that could be perceived as racially motivated, according to agency officials.

The advisory came after the U.S. Embassy in Tokyo tweeted on Dec. 6 that it had received reports of "suspected racial profiling incidents" with several foreign nationals "detained, questioned and searched" by police.

Racial profiling refers to law enforcement officers deciding based on ethnicity that a person is likely to be involved in criminal activity.