At least 138 patients at major hospitals in Iwate and Miyagi prefectures who died in the aftermath of the 2011 quake and tsunami could have been saved under normal medical conditions, health ministry researchers have said.

The team attributed the deaths of 13 percent of the 1,042 patients who died in the 20 days following the disaster to power outages and shortages of materials such as drugs and clean water. The deaths are considered preventable because had there been electricity equipment such as respirators would have worked, and with suitable materials physicians would have been able to carry out surgery, the team said.

Data from Fukushima Prefecture is not included, due to the complicating impact of the nuclear disaster there.

The March 11, 2011, Tohoku disaster left more than 18,000 people dead or missing and triggered the world’s worst nuclear accident since Chernobyl.

Local doctors took part in the research by the Health, Labor and Welfare Ministry.

“Hospitals should map out plans in advance to continue providing medical service during a disaster, such as making up stockpiles on medical items,” said Satoshi Yamanouchi, a doctor who took charge of the survey in Miyagi Prefecture.