Authorities earlier said that nine suicide bombers, believed to be members of local Islamist extremist group called National Thowheed Jamath (NTJ), carried out the devastating blasts that killed 359 people and wounded more than 500 others.
However, Dr Anil Jasinghe, the Director General of the Health Services, said the larger death toll was released as a result of a calculation error.
"The approximate total of the dead would be 253 and not 359 as reported in media," he said.
Jasinghe said that at least 485 injured were admitted to six hospitals throughout the country.
"By 10 a.m. today, the casualty number at hospitals has been reduced to 149. Only 6 had died in hospitals," Jasinghe said.
On April 22, an estimated figure of 280 dead was released.
"As it was not easy to count the correct number of dead due to extensive damages suffered in some cases, the figures issued were all approximate numbers," he said.
Jasinghe said that those who died in the three hotel blasts were mostly beyond recognition as their body parts had suffered comparatively more damages than those who died at church blasts.
Meanwhile, the foreign ministry said the number of foreigners killed has risen to 40, including 11 Indians.