A recent murder case in the southern city Shenzhen has again led to questions over how drivers are vetted, as well as the safety of the services.

The last thing known about this 24 year-old teacher, surnamed Zhong, was that had she had hailed a Didi taxi from the on-line ride-hailing service on Monday evening. She took a photo of the driver's car plate, and left from her home in Shenzhen. After this, she went out of contact.

On May the 2nd, the authorities found her body and arrested the Didi driver.  Police say the driver has admitted to robbing and murdering the girl.

Didi has responded to the incident. In a statement, the company said it was partly to blame, and vowed to adopt more safety measures in the future, including a more comprehensive credit system for the drivers.

It's not the first time that ride-hailing services have prompted safety concerns.

Also in Shenzhen, a report in March found more than 1,600 drivers listed on popular car-hailing apps had criminal records. More than 1,400 drivers were found with a drug history. Cases of harassment and threats from drivers were also reported.

In lieu of the problems, China is set to issue regulations for ride-hailing services later this month.

"There is a basic requirement for every car, every driver and any transportation business that gets on the road. They have to meet the requirements on driving skills, the quality of service as well as the ways they operate. To provide car services that are trustworthy, the parties involved have to shoulder their share of responsibility. It's a universal requirement," said Wang Limei, secretary general of China Road Transport Association.

The coming regulation is widely expected to raise the bar for registering drivers. It will also integrate the ride-hailing services into the existing taxi management system. However, experts warn there could still be problems ahead.

"The ride-hailing services are only providing a platform for information. Unlike existing taxi companies, they have no labor contracts with the registered drivers. So when a legal dispute takes place between a ride-hailing service driver and passenger, it's very hard to really make the platform responsible," said Zhao Zhanling, China Internet Credit Evaluation Center.

By the end of 2015, there were almost 400 million people using ride-hailing services in China. Didi, Uber and other popular apps have gradually stepped up with measures to ensure passenger safety. But to avoid future tragedies, there is still more to be done.