The file photo shows an advertisement of Didi. [Photo: 86shouji.com]

Chinese ride-hailing service Didi has expelled an undisclosed number of drivers in the southern city of Shenzhen who were found to have a history of drug use, mental illness or have significant criminal records.

Didi's action follows a statement issued by Shenzhen transport commission on Tuesday, noting that five ride-hailing platforms had the lax screening processes for drivers.

An initial inspection by Shenzhen's public security department showed that among Shenzhen's app drivers, 1,425 had a history of drug use, 1,661 had significant criminal records, and one driver was mentally ill and caused traffic troubles.

Didi provided personal information on all its drivers to Shenzhen police. After consideration, a list of problematic drivers was sent to the company.

Didi has also asked for police background checks on drivers in other cities to rule out those who might be a risk to the safety of passengers.