Mentawi Islands, Indonesia ? The death toll from a tsunami and a volcano rose to more than 340 Thursday as more victims of Indonesia’s double disasters were found and an official said a warning system installed after a deadly ocean wave in 2004 had broken from a lack of maintenance.

A villager walks Wednesday past a buffalo killed in the Mount Merapi eruption in Kinahrejo, Yogyakarta, Indonesia. A volcanic eruption and a tsunami killed scores of people hundreds of miles apart in Indonesia after spasms from the Pacific “Ring of Fire,” which spawns disasters from deep within the Earth.

Hundreds were still missing after Monday’s 10-foot wave spawned by a massive quake struck the remote Mentawi islands off western Sumatra, where rescue officials — kept away for days because of stormy seas and bad weather — started arriving at the scene to chart the scope of the devastation.

Some wore face masks as they wrapped swollen corpses littering roads and beaches in black body bags. Huge swaths of land were underwater and houses lay crumpled with tires and slabs of concrete piled up on the surrounding sand.

At least 311 people died as the tsunami washed away hundreds of wooden and bamboo homes in 20 villages, displacing more than 20,000 people, said Ade Edward, a government disaster official.

About 800 miles to the east in central Java, the Mount Merapi volcano was mostly quiet but still a threat after Tuesday’s eruption that sent searing ash clouds into the air, killing at least 33 people and injuring 17, said Agustinus, a doctor at the local health department who like many Indonesians goes by one name. A mass burial was planned for later today.

Among the dead was a revered elder who had refused to leave his ceremonial post as caretaker of the mountain’s spirits.

President Susilo Bambang Yudhoyono rushed home from a state visit to Vietnam to deal with the catastrophes, which struck within 24 hours along different points of the Pacific “Ring of Fire,” a series of fault lines prone to earthquakes and volcanic activity.

The first cargo plane loaded with tents, medicine, food and clothes landed Wednesday in the tsunami-hit area, Edward said.

Vice President Boediono toured devastated villages on hardest hit Pagai Utara island and met with survivors and local officials, his office said. At one point, he paused solemnly in front of several corpses in body bags.

The islands lie close to the epicenter of the 7.7-magnitude quake that struck late Monday beneath the ocean floor. The fault line on Sumatra island’s coast is the same one that caused the 2004 quake and tsunami that killed 230,000 people in a dozen countries around the Indian Ocean.

After that monster wave, many countries set up early warning systems in their waters hoping to give people time to flee to higher ground before a tsunami — which can travel hundreds of miles — crashed ashore.

Indonesia’s version, completed in 2008 with German aid, has since fallen into such disrepair that it effectively stopped working about a month ago, according to the head of the Meteorology and Geophysic Agency.

The system, which uses buoys to electronically detect sudden changes in water level, worked when it was completed, but by 2009 routine tests of it were showing problems, said the agency chief, who uses the single name Fauzi. By last month, he said, the entire system was broken because of inexperienced operators.

“We do not have the expertise to monitor the buoys to function as intended,” he said.

As a result, he said, not a single siren sounded after Monday’s quake. It was unclear if any sirens could have made a difference, since the islands worst affected were so close to the epicenter that the tsunami would have reached them within minutes.