CHICAGO, March 15 (Xinhua) -- Chicago-based United Airlines has announced to use colored tags for labeling pet bags after death of a pet dog on one of its flights.

"This was a tragic accident that should never have occurred, as pets should never be placed in the overhead bin," United said in a previous statement. "We assume full responsibility for this tragedy and express our deepest condolences to the family and are committed to supporting them."

United pledged to provide better care for pets on board its flights. "To prevent this from happening again, by April we will issue bright colored bag tags to customers traveling with in-cabin pets," it said in a statement on Wednesday.

The incident took place Monday night on board a three-hour flight from the southern city of Houston to New York City. A carrier containing a French bulldog was on the ground sticking out into the aisle, and the owner was told to store it in an overhead bin. Upon arrival the dog died.

The incident drew a spotlight on the United's pet care record, which according to official figures is the worst in industry.

The U.S. Department of Transportation said 24 pets died or was injured last year while flying on U.S. carriers, 18 of which were on the United flights.

The district attorney's office in Harris County, Texas on late Wednesday said its animal cruelty division is working with the county's animal cruelty task force to investigate the death of the bulldog on the United flight from Houston.

Prosecutors said in a statement they won't decide whether or not to press charges until the investigation is completed.