The system fault occurred just one day before 11 September, which was expected to be one of the most nervous trading days of recent years.
The IT department at a large London-based financial services company reported the failure to staff on Tuesday morning. "Reuters services are still unavailable. Most prices on Reuters Terminals have not updated since 09:19 and cannot be relied upon. The fault is affecting 50% of Reuters positions worldwide. We still have no information at present about when services might be restored," it said.
The failure could have had serious consequences, industry experts said, as Reuters is by far the largest supplier of data to the equity markets.
A Reuters spokeswoman said the outage, which delayed or deleted real-time information being received by customers in Europe, the Middle East and Asia, lasted about four hours. "Our global team investigated the problem [which they discovered at 6.45am] and all the real-time information was restored by 11am," she said.