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Lyft's new bike-sharing system in the Bay Area, dubbed Bay Wheels, includes black-and-pink electric-assist bicycles powered by a battery on the bike's frame. These units used to be part of bike-sharing program Ford GoBike, similar to New York City's Citi Bike. Now, it appears some are becoming a bit too hot to handle.

The San Francisco Examinerreported on Wednesday that a passerby saw flames coming from a bike parked in an official Bay Wheels dock in the Lower Haight area around noon. Apparently a separate Lyft e-bike caught fire over the weekend, also in San Francisco, with the fire emanating from its battery.

Last week a Lyft e-bike with a burning battery was reported on the UC Berkeley campus, across the bay from San Francisco.

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"Out of an abundance of caution, we are temporarily making the e-bike fleet unavailable to riders while we investigate and update our battery technology," said a Lyft spokesperson in an emailed statement.

The bikes have been pulled in San Jose, San Francisco, and Oakland -- the only locations that offer the new Bay Wheels e-bikes. The bikes first arrived in San Jose in June and in San Francisco and Oakland in July.

Before the new branding and e-bikes were unveiled, Motivate's bike-sharing fleets (Lyft acquired Motivate and its bicycles last year) had a braking problem and the old e-bikes had been pulled off the streets at three cities across the U.S. The new Bay Wheels bikes finally replaced those bikes, which had been unavailable since April.