The Changping subway line in Beijing resumed operations on Friday, except for a section where a rear-end collision took place on Thursday evening, leaving many injured. More efforts will be taken to guarantee the safe and normal running of the system in snowy conditions, the municipal traffic authority said.

A subway train crashed into another that had made an emergency stop at around 7 pm on Thursday, the Beijing Municipal Commission of Transport said in a notice on Friday.

All rescue and evacuation work was completed by 11 pm on Thursday. A total of 515 passengers were sent to local hospitals for examination and treatment, including 102 with fractures. There were no fatalities. As of 6 am Friday, 423 people had been discharged from the hospital, with 25 still under observation and 67 receiving treatment, the notice said.

A preliminary investigation determined that the underlying cause of the crash was slippery tracks during frigid and snowy conditions. The approaching train, which was going slightly downhill, skidded during braking and was unable to stop in time.

It slammed into the last carriage of the train just ahead. Both were traveling from Xi'erqi Station in Beijing's Haidian district to Life Science Park Station in Changping district during the capital city's evening rush hour.

Videos and photos posted online by netizens on Thursday and Friday showed that the connection between the last two carriages and the rest of the leading train had been severed. Some passengers broke windows to access fresh air while others were seen walking along the tracks.

"We extend our sincere condolences and deep apologies to the passengers who were stranded, frightened and injured in this accident. We will make every effort to treat the injured and handle the aftermath," the notice from the city's transport commission said. "We will improve extreme weather operations and emergency response plans to ensure the safety of urban operations."

The Changping line was operating normally on Friday except for affected sections. Buses have been provided between the impacted subway stations, Beijing Subway said in a notice on Friday.

To ensure the safe operation of trains in extreme weather conditions, all subway trains of the Changping line operating above ground or on elevated tracks are operating in manual mode at lower speeds. Along the subway line routes, bus services have also been increased, the notice said.

Passengers who left the scene of the collision on their own before and during rescue and evacuation operations but who later experienced physical discomfort can contact the subway company, which will pay for medical treatment and recovery expenses, it added.

After the accident, Yin Li, Party secretary of Beijing, and Yin Yong, the city's mayor, rushed to the site immediately after the accident. District officials, as well as authorities from the city's transport, traffic management, subway and bus departments, were also on hand to conduct prompt rescue work.

The Beijing municipal government set up a team on Thursday night to investigate how the accident took place and identify and hold accountable those parties responsible and to process injury and damage claims.

Beijing has been experiencing heavy snow and cold temperatures since Wednesday, with the depth of snow in most areas nine to 12 centimeters, the city's meteorological authority said.

A cold wave has been affecting North China of late.