Police Chief Danielle Outlaw and Assistant Chief Ryan Lee say the Portland Police Bureau has suspended use of "flash-bang" grenades after reports that multiple people were severely injured as officers drove back a crowd of antifascist protesters on Aug. 4.

Outlaw and Lee say the devices should not have caused injuries if they were used properly and operated as intended.

"They're trained to fire arial distraction devices," Ryan said at a press conference Monday afternoon. "They're trained to fire those not directly at individuals. They're trained to fire them over the crowd. Those devices are designed so that if you have a 15 degree up angle… they should actuate roughly 20 feet above that person's head."

One woman says she was hit with the first explosive launched by police at the crowd of protesters standing near the intersection of Southwest Naito Parkway and Southwest Columbia Street. She went to an urgent care clinic with third-degree burns on her arm and chest.

An image of a bike helmet with the canister of a flash-bang grenade lodged in the back was posted on Twitter shortly after the protest broke up. According to Raw Story and other accounts on social media, unconfirmed by WW, the man who had been wearing the helmet had burns and lacerations to the back of his head and had to be hospitalized.

Police say they do not understand how the explosive riot control devices could have caused the injuries that have been reported.

"We've temporarily suspended the use of one of the particular devices that we think, if it was connected to that helmet, so we could take a look at whether or not there were any unintended consequences or any malfunctions," says Chief Danielle Outlaw.

Lee expanded on the temporary suspension of the grenades.

"We've removed from service the arial distraction device until we can conduct some tests to make sure that they're performing within the way that we expect them to," he said. "We would ask that the owner of that bike helmet come forward so that we can examine it, because if that image is in fact as it appears, that would not be consistent with what we would expect that device to do. We need to understand why and how if that is indeed an accurate image."

Neither Lee nor Outlaw could answer reporters' questions about what a layperson might call the "arial distraction device" used by police to disperse the crowd Saturday. But the explosive devices that emit a bright light and a booming sound are often called flash-bangs, stun grenades, or concussion grenades.

Despite the police bureau's insistence that the grenades should not have caused injuries, plentiful evidence exists documenting that the devices frequently cause injury and can even kill. The American Civil Liberties Union of Oregon has repeatedly urged the Portland police to stop using these types of explosives on crowds of protesters because of the potential for serious injuries.