Up to 1,000 bodies are thought to be in the area, but their retrieval has been delayed because of radiation fears.
Staff are working to bring the nuclear plant under control, after cooling systems at three reactors were knocked out by the quake.
More than 300 police in protective gear are searching for bodies.
It is the first time an operation to find those killed by the earthquake and tsunami has been carried out in the 10km (six-mile) zone around the plant.
Police said falling radiation levels had made it possible.
"The search started around 1000 and will continue until sunset," a police spokesman said. "It's difficult to estimate how many people are still missing in the area. We have to go and find them as soon as possible.
"If we find bodies contaminated with high levels of radiation, we will wash the remains before we take them to a morgue."
The earthquake left 13,456 people dead and another 14,851 missing. More than 150,000 have been made homeless.
The government has promised to improve its communications after remarks by a government adviser angered evacuees from the plant area.
The adviser quoted the prime minister as saying evacuees would probably be unable to return home for 10 or 20 years - a remark the prime minister denied making.
''We are looking into how we can properly convey the information" to evacuees, top government spokesman Yukio Edano said.
''As communication has not been sufficient, we need to take this seriously.''
On Monday, the government said it would expand the evacuation zone around the plant. Currently a 20-km (12-mile) evacuation zone and a 20-30km "stay indoors" zone are in place.
The government now plans in the coming weeks to evacuate residents in villages outside the 20km zone where elevated levels of radiation have been found.
Work to stabilise the nuclear plant is continuing. Engineers are pumping water into three reactors to cool fuel rods after cooling systems were damaged by the earthquake.
They have discharged waste water with low levels of radioactivity into the sea to make room to store more highly contaminated waste water on site.
Water needs to be removed from the basements of reactors 1, 2, and 3 before vital work on the cooling systems can begin.
But on Thursday operator Tepco (Tokyo Electric Power Company) said that water levels in the basement of reactor 2 were continuing to rise, even as some was being pumped to storage.