Broadband provider Orange is refusing to reveal the precise cause of a massive broadband outage that began on Monday.
Over 100,000 Orange broadband customers were affected by the outage, which began at 4pm GMT on Monday, according to an Orange spokeswoman. Full service was not restored until 6.30am on Wednesday morning.
Orange has apologised to those affected and blamed the problems on a "network equipment failure". However, it refuses to say whether it was its own equipment that had failed, BT equipment, or a third party's.
Orange has installed its own equipment in many BT exchanges, through the process of local loop unbundling (LLU). This means it can manage the lines itself and potentially offer a wider range of broadband services than are available from BT through Openreach, BT's network operating arm.
LLU should bring more competition to the UK's telecoms market. BT recently came under fire from the telecoms adjudicator Peter Black because just 78 percent of newly unbundled lines were being delivered successfully.
BT denied on Wednesday morning that any of its equipment had caused the Orange outage.
"There are no problems with our broadband network at the moment — Openreach is working fine. There are no problems at our end," said a BT spokesman.
A source close to the problem told ZDNet UK that the outage may have been caused during an upgrade of Orange's network equipment.
Orange's move into unbundling has not been smooth. The company suffered problems with its broadband service in August after another "equipment failure".
Orange merged with Wanadoo back in May, after which Wanadoo's broadband service was rebranded under the Orange name. Wanadoo had also been criticised by its users, some of whom were so disgruntled they set up a Web site in April to discuss Wanadoo's alleged service shortcomings.