HONG KONG/MADRID (Reuters) - China’s biggest bank, Industrial and Commercial Bank of China (ICBC), has called on Spanish authorities to release three of its workers being held in jail as a court investigates money laundering allegations at its Madrid branch.

A woman walks past a Spanish Civil Guards at the headquarters of Industrial and Commercial Bank of China (ICBC) during a raid in Madrid, Spain, February 17, 2016. REUTERS/Juan Medina

A Spanish judge’s decision to grant bail to only three out of six staff detained after a raid on ICBC’s Madrid offices last week was incomprehensible, it said in a statement on Thursday.

The Chinese bank had not previously commented on the case beyond stating it was cooperating with the authorities and always strictly implemented money laundering regulations.

The Spanish investigation is centered on allegations of funds transferred by a criminal group via the bank to China.

Six people were arrested as part of the probe and jailed, a precautionary measure allowed under Spanish law while investigating judges work on a case. Three were released after paying bail of 100,000 euros ($110,340).

Spanish courts can refuse bail on the grounds that a person could be a flight risk, or if they are concerned that evidence might be destroyed.

ICBC said one of those detained was a former chairman of the bank’s Madrid branch, who had been transferred to Luxembourg and had returned to Spain on Feb. 17 when the police raid began.

“If he really wanted to abscond, he wouldn’t have traveled from a place outside Spanish jurisdiction ... back to Madrid,” ICBC said, adding that one of the female workers still in jail was suffering from poor health.

A spokesman for Madrid’s judicial authorities declined to comment. A legal source familiar with the case said ICBC could file an appeal to contest the judge’s decisions. Spain’s foreign ministry also declined to comment.

It is not the first time Spanish legal investigations have caused tension between the two countries.

China bristled in 2014 when a judge issued arrest orders for former top Chinese officials as it probed a complaint by a Tibetan-Spanish monk who accused the former leaders of genocide, torture and crimes against humanity.

It was one of several cases carried out by Spanish judges using universal jurisdiction, the principle that crimes against humanity, torture and genocide can be prosecuted across borders.

Spain’s High Court later dismissed the Chinese case after the government hurried through changes to the law, restricting investigations to cases with a very strong Spanish link.

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