By Pan Yan

The recent arrest of Lo Hsien-che, a senior Taiwanese general who allegedly spied for the Chinese mainland, was not the first time such a scandal raised questions about spying across the Straits.

For decades now, experts have said, cross-Straits spying has been common and this new case will not have a significant impact on the relationship between the mainland and Taiwan.

Over the years, authorities on the Chinese mainland have uncovered several cases in which double agents were accused of betraying the mainland.

Taiwan's spying activities on the mainland could be categorized into two areas. They either recruit people on the mainland, especially in-service military officers, to spy for Taiwan, or to conduct spying activities on the mainland under the cover of doing business.

Here are some of the most serious cases uncovered on the mainland.

Liu Liankun

Liu, a former major general in the People's Liberation Army, was executed in 1999 after he was found spying for Taiwan.

Liu, born in 1933 in Qiqihaer, Heilongjiang Province, was head of the ordnance department of the General Logistics Department in the People's Liberation Army (PLA) for six years.

According to a 2004 report in the Hong Kong-based Wen Wei Po, Liu was recruited by Taiwan in 1992.

He leaked important information to Taiwan including the locations of mainland missiles over a seven-year period.

The report said Liu provided Taiwan with information about mainland military drills during Taiwan's "presidential election" in March 1996.

Fewer than 10 people on the mainland knew about the missiles. Another officer involved, Shao Zhengzong, a PLA colonel, was arrested.

The report also said that officials in Taiwan's military intelligence bureau squeezed Liu to get as much information as possible so they could earn quick promotions, which lead to Liu's exposure.

Liu Guangzhi

Liu Guangzhi

Liu, another senior PLA officer, was executed for spying for Taiwan five years later.

Liu, born in 1947 in Zhaoyuan, Shandong Province, was a major general in the PLA and a former president of the Beijing-based Air Force Command College, before he was arrested.

According to a 2004 report on Hong Kong-based ifeng.com, Liu was recruited by a former colleague surnamed Jia, at the Air Force Command College. Jia worked for Taiwan after he left the army and joined a company owned by a Taiwanese named Li Yun-pu, a former colonel in Taiwan's MIB.

Liu turned over plenty of information to Taiwan about the missile deployment, training and other key facts.

Comments made by former Taiwan leader Chen Shui-bian led to Liu's exposure.

In 2003, Chen said publicly that the mainland deployed 496 missiles in five locations aimed at Taiwan.

Soon after that, Li was arrested in Nanjing, Jiangsu Province when he went to meet Gao Guoning, another spy for Taiwan.

The Ministry of State Security in Beijing arrested more than 20 Taiwan spies who conducted spying activities in the name of doing business on the mainland. They discovered that Liu and his son, a senior PLA officer in the logistics department, were both working for Taiwan.

A report said that after Liu was arrested, the special investigations team found a large pile of cash in Liu's office and that other people involved.

Wo Weihan

Wo, a Chinese mainland citizen, was executed for spying for Taiwan in 2008.

According to a 2008 report in the Chinese edition of the Global Times, Wo, born in Qiqihaer in Heilongjiang Province in 1942, earned a master's degree at the Institute of Biophysics, Chinese Academy of Sciences, in 1984. He went to Munich, Germany for further studies in 1987.

The report said Wo's financial status was in trouble at the time he was studying abroad and he was recruited by Taiwan.

Wo did not return to China after he earned a doctoral degree in Germany in 1991. He moved to Austria to do business. He visited the Chinese mainland several times to collect information in the 1990s.

He registered a pharmaceutical company in Beijing and called himself "chief scientist" to disguise his true identity, the report said.

Wo succeeded in learning about key PLA weaponry and recruited several other mainland citizens to spy, including Guo Wanjun, a missile expert in China.

Wo learned about the mainland's missile technology from Guo. Wo then passed the information to Taiwan agencies based in Europe. In 2005, State officers arrested Wo and Guo.

Additionally, in 2003, People's Daily online reported that mainland authorities arrested 36 Taiwan businessmen who were allegedly spies. They were paid to share information to Taiwan.