A study says hundreds of police departments in Texas and California failed to report officer-involved shooting deaths in the past decade.

The Houston Chronicle reports (http://bit.ly/2dGaPok ) a study by Texas State University in San Marcos found registries created by the two states to report all in-custody deaths did not list about 220 use-of-force fatalities in Texas and 440 in California from 2005-2015.

The Texas and California attorney general's offices and police officials in both states have confirmed many cases were missing.

Texas State University professor Howard Williams says his research is not about "blaming anyone" but adds a lack of data on such shootings makes it difficult to improve training and change policy.

Texas and California are the only states to require reporting of all in-custody deaths, including jail deaths and officer-involved shootings.