New York City's police commissioner says officers have purposefully not written tickets or made some low-level arrests in the nearly three weeks since two officers were fatally shot.

Commissioner William Bratton said Friday that no police union gave any official instruction to slow police action. He says the arrest and summons numbers are increasing and should return to normal in the next week or so. They plummeted more than 90 percent after the Dec. 20 shootings.

He says crime remains down overall, and he's not concerned that the recent slowdown has affected safety.

One officer was suspended for insubordination. No other officers are facing any other discipline because of the slowdown.

Bratton says he does not know why it happened. He has said morale among some officers is low.