Uber victim of a computer system breach

SAN FRANCISCO - Uber's computer system has been breached and the company has alerted authorities

The ride-hailing company said in a tweet that it was "in response to a cyber security incident".

The hack was revealed in a message posted on Slack, according to two people familiar with the matter

who spoke on condition of anonymity because of the sensitive nature of the incident.

"I hereby declare that I am a hacker and that Uber has been the victim of a data breach," he said.

This was followed by a flurry of reaction emojis, including dozens showing what appeared to be a siren symbol.

  Some systems, including Slack and internal tools, were temporarily disabled due to the hack, people said.

Uber previously suffered a breach in 2016 that exposed the data of 57 million people around the world.

Uber, which is based in San Francisco, employs thousands of people worldwide who could be affected by the hacker's system.