In brief: Electronics giant Xiaomi might be best known for its mobile phones, but electric scooters are just one of the many other products it makes. These two-wheelers are used by several services in the US, including Lyft, but the Chinese firm isn’t happy with the ride-sharing company and has sent it a cease-and-desist letter.

The scooters are just one type used by US companies, including Spin and Bird. But, as reported by TechCrunch, Xiaomi has objected to Lyft referencing its brand in ads and other documentation relating to its shared scooter business.

“We also do not condone Lyft’s unauthorized modification or retrofitting of our electric scooters for general public use,” Xiaomi wrote in a letter, obtained by the publication.

Xiaomi warns that unless Lyft stops using its scooters “that have been modified without our consent in public scooter rentals,” it may launch legal action against the firm.

“Lyft’s modification to any scooters originally manufactured by Xiaomi without our knowledge, participation, or approval undoubtedly exposes Xiaomi to serious legal risks and liabilities for consumer safety and product liability,” states the letter.

In response, Lyft says it is unaware of using of Xiaomi’s trademarks in its ads and said any modifications meet safety regulations. “We have no intention of using any other company’s trademarks in advertising our scooters, and are not aware of any instance of having done so with our existing suppliers,” a Lyft spokesperson said. “We will address these concerns with them directly. Safety modifications, including slowing scooter speeds, have been made to satisfy local regulatory guidelines.”

It’s not clear why Xiaomi has singled out Lyft when other firms use their scooters, though Bird said it has an exclusive deal with the company to use them. However, an executive with another scooter rental company told TechCrunch it also had a contract with Xiaomi.