Several airports across the country have tightened up security checks after the blast at the Beijing Capital International Airport Saturday triggered by Ji Zhongxing, a disabled petitioner from Shandong Province.

"We have implemented a security plan to prevent explosions at the airport and strengthened safety checks on passengers," a press officer with the Beijing airport told the Global Times Monday, adding that the airport has not been greatly affected by the blast.

The two airhubs in Shanghai have also upgraded their security, with several terminal gates closing temporarily. Passengers have been told to get to the airport half an hour earlier, according to a Monday report by the Oriental Morning Post.

Ji Zhongxing, a 34-year-old wheelchair-bound petitioner from Juancheng, Shandong, detonated a homemade explosive device at the Terminal 3 of the Beijing airport Saturday, injuring a plice officer and himself. Ji is now under criminal detention.

Ji's extreme act came as a result of depression after he failed to receive compensation from the government of Dongguan, Guangdong Province, after he was allegedly paralyzed by a beating by local security officers in 2005.

The Dongguan government denied Ji's claims Sunday, saying that the paralysis was caused by a traffic accident in which Ji collided with those officers and fell down. His lawsuit for compensation was also dismissed in 2007 by a local court for lack of evidence.

After several failed petitions, Ji was found missing on Saturday by his father, Ji Tairong. The father then called him, but he said it was just a normal outing, reported by the Jinan-based Qilu Evening News.

"Ji left by a taxi under a friend's help, and took a bus in Juancheng to Beijing," an official in the Juancheng public security bureau said.

"He didn't tell anyone about that. Our family is shocked by what he did as he has always been easygoing with a mild temper," Ji's sister-in-law, surnamed Xu, told the Global Times.

While some are investigating what officers in Dongguan may have done to Ji, many are questioning where the explosive device came from.

Police found a handwritten explosive recipe in Ji's directory left at home and contact details from some air rifle vendors.

"There is no explosive at home. We don't know where he got it. But I don't think he could buy them in our township as it is not likely for him to go out without other's help," Xu said.

The bus station in Juancheng claimed that no explosives had been found when Ji went through the security check. The local police are still conducting further investigation, the China Youth Daily reported Monday.

"Ji will face at least three years in prison. But the punishment could be lenient as he didn't cause any deaths," Wang Dianming, a lawyer at the Beijing Tongchuang law firm, told the Global Times.