Colorful confiscated bikes are lined up at a parking lot in Shanghai, China March 1.
Beijing, CNN CNN  — 

They seem like a perfect solution to China’s traffic-clogged streets and toxic air: Bikesharing schemes.

They’ve exploded in popularity in past 12 months, with brightly colored bikes owned by several different companies flooding China’s major cities. Residents can rent them via apps on their smartphones.

But some local authorities say the bikes have become a nuisance and one Shanghai district has confiscated almost 5,000 bikes and impounded them in a parking lot. Striking aerial photos of the orange, yellow, blue, green bikes were widely shared by Internet users in China last week.