Flock Safety said Wednesday it has tightened the rules for searching its database of billions of license-plate scans ahead of a Senate hearing set to scrutinize whether the company’s rapidly expanding surveillance network has outpaced meaningful safeguards.

At the outset of the hearing, Sen. Josh Hawley (R-MO) said Flock issued him a letter saying it changed the information police officers and other users must provide to justify searches. Users were already required to state a reason, but the company acknowledged that the old free-text system yielded explanations that were not always specific.