Nearly all of the 43 bus companies in Shenzhen have unsanitary buses, a three-month inspection on the city's buses has found.

The inspection, launched by the municipal communications bureau last quarter, spotted 682 buses with dirt, smears of grease, litter, cockroaches or stifling and stagnant air.

In an effort to expose and penalize the bus companies, the bureau publicized the names of 16 companies whose buses were the filthiest. Big names such as Shenzhen Bus Group and Yunfa City Bus Company were on the blacklist.

Two groups of traffic officials carried out the random inspection on the buses. One group found that 315 out of the 500 buses inspected failed to meet sanitary standards set by the government. The other group reported 367 dirty buses.

The city's cleanest buses are those running between the airport and downtown. Only 2 percent of these buses failed to meet the sanitary standards, the inspection found.

Unsanitary buses have long been a complaint of Shenzheners and a headache for the government.

"Some bus drivers refuse to switch on air conditioners during cooler months in order to save fuel costs. That makes the air really smelly, because the windows are closed," said a passenger by the surname of Zhang.

The municipal communications bureau has promised to clean up the city's buses by enhancing supervision. Passengers with complaints about the bus services can dial the bureau's hotline 8322-8000.

Editor: Yan