CLEVELAND, Ohio -- A few hours after the first Bird electric scooters were spotted in Cleveland, the City expressed concern in a statement Friday evening, saying the scooters raise "important safety issues that need to be fully explored and properly addressed with the City."

A flock of 100 electric share-scooters landed Friday morning in the downtown, Flats and Ohio City neighborhoods, but as of Saturday morning, "Bird Rides, its agents, or customers, are not permitted to place property on the sidewalks of the City without obtaining a permit."

While that does not violate Bird's user agreement, which clearly advises to ride in streets and bike lanes, - not on sidewalks - the City also said scooters are to be removed by Bird Friday evening and not reintroduced to public sidewalks or parks on Saturday.

"Unattended scooters on the sidewalks are subject to removal and impoundment," law director Barbara Langhenry said Friday in a statement.

After finding a scooter and unlocking it with the app, Bird riders have to accept a user agreement that they will ride in streets and bike lanes, - not on sidewalks - are at least 18 years old, are the only one riding the scooter, are wearing a helmet and aren't riding with a briefcase, backpack or bag.

"We have seen these scooters parked unattended on the sidewalks of the City," the City said in its statement. "Please be aware that Bird Rides, its agents, or customers, are not permitted to place property on the sidewalks of the City without obtaining a permit."

In other cities, users have broken Bird's rules, sometimes resulting in injury.

"We believe that you would agree that the placement of unattended, commercial, electric scooters on City sidewalks raises important safety issues that need to be fully explored and properly addressed with the City," read the message addressed to Bird Rides, Inc.

"Please remove any scooters from the public rights of way, which includes streets and sidewalks, and other public property tonight, August 10, 2018. Based on your representation that the scooters are removed nightly, this should not be a problem. Because your business model depends on the scooters being left unattended on the sidewalks of the City, please do not 'reintroduce' the scooters to the public sidewalks or public parks in the morning."