The European Union cut off vital funding to a Gaza power plant, forcing it to shut down the last of its generators and darken tens of thousands of Palestinian homes. The shutdown Sunday was another blow to residents of the Gaza Strip, where Hamas has been governing, largely under international isolation, since June. The power plant already cut electricity to large swaths of Gaza last week after Israel closed a fuel crossing into the coastal territory, citing security concerns. Israel reopened the Nahal Oz Crossing Sunday, but the plant's Israeli fuel supplier said the European Union had instructed it not to deliver new supplies because it would not guarantee payment. "Fuel supplies will resume if and when the European Union or another credible source notifies us that it will guarantee payment for the power station's fuel," Israel's Dor Alon fuel company said in a statement. Alex de Mauny, a spokeswoman for the EU's executive branch, confirmed the EU would not finance Sunday's fuel payment. "In light of the security situation, we've decided to take stock of all of our mechanisms and systems, including auditing, monitoring and funding flows," de Mauny said. The assessment will be complete by Tuesday evening, she said. Gazans initially were unfazed by the outages, because power reserves are always so thin that consumers are used to living without electricity for about five hours a day. But as the shortages dragged on for a third straight day, nerves began to wear thin. The din of private generators outside every shop on Gaza City's main commercial street filled the air as Naim Hamdan, a civil engineer, recounted how he sent home his 25 employees to conserve fuel. European officials were caught off guard by the power shortage, mistakenly believing the plant had enough fuel for another two days, an EU official told The Associated Press. The official spoke on condition of anonymity according to EU regulations. The government of Palestinian Authority Chairman Mahmoud Abbas, formed in the West Bank after Hamas took over Gaza, charged the group with responsibility for the power shortage. The EU ceased payment "because Hamas took over the electric company and started collecting the revenues and taking them to its pocket," PA Information Minister Riad Maliki told reporters at a press conference Sunday. The EU, however, did not say its decision was connected to Hamas. In turn, Hamas lawmaker Yehia Musa accused Abbas of a "dirty conspiracy" to persuade international donors to cut off electricity to Gaza in an attempt to discredit Hamas. The Gaza Generating Co., which powers 25 percent of the coastal strip, cut power to nearly half of Gaza's 1.4 million people on Friday after Israel closed the fuel crossing. It shut off the last of its four generators Sunday after its fuel reserves were depleted, extending the power outage even further. Gaza Generating's chief executive, Rafik Malikha, urged all relevant officials "to end this crisis situation in Gaza now." Although private generators and sporadic supplies from the Israeli and Egyptian companies that power the rest of the strip have eased the blackout, affected neighborhoods and cities will be without electricity for at least 12 hours a day, Malikha said. Since Hamas came to power in Gaza two months ago, Israel and Egypt have sealed the border crossings into Gaza except for vital humanitarian aid. The international community has largely isolated Hamas while embracing Abbas's West Bank government, hoping to prevent further gains by Islamic terrorists. The closure led the UN to warn last week that Gaza will soon become entirely dependent on foreign aid and face "disastrous consequences" if the territory remains sealed off, while a Palestinian business group estimated that at least 120,000 Gazans could lose their jobs if the border crossings remain closed.