Two men have been arrested on charges of masterminding a government office blast that left four people dead in southwest China's Yunnan Province in May, local police announced Tuesday, acknowledging they had wrongly accused another man killed in the explosion.

The blast, which also injured 16 other people, took place at a housing demolition office in Baihetan Township, Qiaojia County, Zhaotong City on May 10, when officials were signing compensation agreements with residents of Yibo Village over the demolition of their homes.

Deng Deyong and Song Chaoyu, both 43 from Yibo, had confessed to planning the blast because they were not satisfied with the demolition compensation, the Zhaotong Municipal Public Security Bureau said in a statement.

They confessed that they found 26-year-old Zhao Dengyong at a local labor market and gave him 100 yuan (15.9 US dollars) to carry out their plan on May 10. They used a mobile phone as a remote control device and detonated the explosives Zhao was asked to carry when they saw that Zhao had entered the housing demolition office, the statement said.

Local police had previously announced that Zhao, who was killed in the blast, was the suspect, because explosives had been found in his black backpack.

The conclusion triggered widespread doubt, as Zhao was not a villager in Yibo and he had no ties to the housing demolition. But police insisted that Zhao had done so to take revenge on society, citing cynical words exposed in his online chat logs and diary.

The two true culprits were finally found after police discovered new important clues, including new DNA evidence and fragments of a circuit board, according to Tuesday's statement.

Local police acknowledged that Zhao was not involved in planning the blast and that he himself was also a victim, the statement said.

They have offered their sincere apologies to Zhao, Zhao's family and the public for previously releasing misleading information, it said.