A salvage crew finally managed Thursday to board the stricken MV Rena cargo ship, which has already spilled oil and containers off the coast of New Zealand. The crew was checking the possibility of pumping oil from the ship before the vessel breaks up and sinks into the sea.

The weather cleared just enough to allow three crew members to be lowered on to the MV Rena by helicopter around 10 a.m. The 47,000-ton cargo ship had hit the reef off the coast of Tauranga and spilled oil in what is fast becoming one of New Zealand's worst maritime disasters. Oil was drifting ashore in moderate and heavy quantities from Papamoa to Maketu. Oil recovery teams were already out on the beaches to start cleanup operations, according to Maritime New Zealand.

The salvage crew was checking the ship's stability and whether it was still possible to pump out the remaining oil in the cargo hold. Officials have also looked at other possible measures to stop the oil, including liquefying the remaining oil before it can be pumped out.

The Rena has sustained a substantial vertical crack that threatens to tear it apart.

"The reality is the vessel could break up at any point," Steve Jones, spokesman for Maritime New Zealand, told The Associated Press. "Conditions are very calm out at the moment. ... If we're going to get oil off before the ship breaks up, today's the day."

The MV Rena oil spill has already been dubbed by New Zealand's environment minister as the country's biggest maritime environmental disaster. Officials believe the there have been at least 390 tons of heavy fuel oil that have already leaked from the ship. There are about 1,870 tons of oil and 220 tons of diesel estimated still on board the ship.

The cleanup effort will be a massive undertaking that is hampered by the weather and the fear of chemical hazards aboard the ship. The government is asking volunteers to help with the cleanup effort and has set up muster stations along the coast.

"We are still expecting this to be a long process. There will be plenty of opportunity for people to assist," Transport Minister Steven Joyce said.

"I met with the salvage master this morning; they are very pleased about moving in after the weather they had and putting that first crew out there today."

"This is not going to be a simple exercise," he said.