Many IT managers in Sydney's CBD have had to put their power contingency plans into effect today as electricity to sections of the city was cut off thanks to a fire in an underground cable tunnel.

The fire, which occurred on Monday evening, was contained but not before lines were burnt and power to many city buildings was cut.

Some of the buildings affected included the Westin Hotel and the MLC Centre, which houses such residents as legal firm Freehills and the US Consulate Generals.

Early morning calls by Computerworld to the US consulate were greeted by an engaged tone. A few levels below, the Freehills IT department was working overtime. A phone call to speak to the IT department was greeted by a flustered front desk: "They are right now in emergency mode and it is the wrong time to call [to speak to them]."

Other businesses were more fortunate. Geoff Pritchard, an IT administrator at the Coal Services board, whose power has since been restored, said his business was only slightly affected.

"Our servers were shut down overnight [automatically due to the power failure]. I had to spend 30 minutes this morning checking over the machines and restarting all services," he said. "We weren't really affected by the power failure other than a few blown power supplies in our client machines."

According to security guards posted around the MLC Centre, Energy Australia is now in the process of restoring power to office and retail areas situated within the centre - both of which have been closed since this morning. Westin Hotel staff have also been informed that power should be fully restored to the Hotel by 5pm this afternoon. In the meantime, the Hotel is using its diesel generator to provide power and carry on business "as usual", a staff member said.

Spokespeople for two other businesses in the vicinity of the fires, Nestle and PricewaterhouseCoopers, said staff had not experienced any power problems.