NETWORKING firm 3Com said its European HQ was damaged when an oil depot exploded yesterday morning. It said that its site, in Hemel Hempstead, Hertfordshire, had around 300 people working there, but none of its employees have suffered injuries. The 3Com site is a quarter of mile from the site of the fire, which continues to burn one day later. The fire services are expected to start dampening down the fire at daylight today. Meanwhile a pall of smoke hangs over the south east of England.