Nervous commuters returned to Shanghai's subway system Wednesday, one day after a wreck that sent more than 270 people to hospitals.

Transport officials in the Chinese city say a panel has been set up to thoroughly investigate the cause of the accident, and that outside experts will be consulted. They blamed the rear-end crash on the failure of signaling equipment made by the same company as the equipment involved in a July train wreck that killed 40 people.

Subway riders Wednesday said the transit line needs better safety systems.

One rider said automatic emergency systems should be standard on every train.

But another passenger said commuters have to go back on the trains to get to work.

The 26-year-old said accidents like the one on Tuesday do not happen often.

However China's Xinhua news agency said the crash was the third system failure on the subway line in the past two months. On July 28, signal failures sent a train heading in the wrong direction. Five days later, another train stalled on the same line.

Health officials said hospitals treated 271 people injured in the latest accident, most with cuts and broken bones. Many other lightly injured people were seen making their own way home from the scene.

No one was killed, but subway officials said it was the “darkest day” in the history of Shanghai's subway system.

They said the accident, in which one train slammed into the rear of another train that had stopped, was the result of a failure of signaling equipment built by CASCO Signal, which is partly owned by the French transport and power giant Alstom.

Signaling equipment built by the same company was blamed for July's fatal train crash in the city of Wenzhou near Shanghai. That accident prompted an outpouring of public anger and questions about whether China is sacrificing safety in the interests of rapid economic development.

Chinese state media say the company has been involved in at least 28 subway signaling projects across China.