TOKYO — Nearly four years after Japan’s massive March 2011 earthquake and tsunami, the country has made “significant progress” toward stabilizing and decommissioning the ravaged Fukushima Dai-ichi nuclear power plant, international nuclear inspectors said Tuesday.

However, the nearly 160 million gallons of contaminated water stored on-site pose massive logistical challenges, and examiners strongly urged Japan to consider controlled discharges of the liquid into the Pacific Ocean once it is treated.

The situation at the crippled plant remains “very complex” and “the benefits (of discharges) could be very, very huge” said Juan Carlos Lentijo, who led the team of 15 inspectors from the International Atomic Energy Agency on a nine-day mission that follows surveys in April and November 2013.

Japanese officials have been reluctant to take such a step at the plant 160 miles northeast of Tokyo, fearing it might further antagonize local fishermen and other residents affected by the initial accident and its aftermath.

In the past year, Japan has succeeded in removing spent and fresh fuel from one reactor, Unit 4, and reduced the inflow of groundwater into the facility. It has also taken steps to clarify what entities are responsible for particular jobs, the IAEA team noted.

But about 80,000 gallons of groundwater continue to enter the plant per day, and building and maintaining storage tanks is increasingly taxing for the 7,000 workers toiling at the site, Lentijo’s team noted. In January, a laborer in his 50s who was inspecting an empty, 33-foot-tall storage tank fell into the vessel and died.