1997. In 1991, seven conscripts of the Karelia Brigade drowned when their BTR-60 sank at Taipalsaari during an amphibious exercise because the vehicle was loaded incorrectly (top-heavy) and the roof hatches opened. The usual nicknames for BTR-60 amongst the Finnish conscripts were Petteri (a male name), after the initials BTR, and Taipalsaaren sukellusvene (Taipalsaari Submarine) after the 1991 incident. Poland Milicja Obywatelska (MO) operated several BTR-60PAs. They were used by ZOMO riot control units. The Polish Army also received a dozen BTR-60PU-12s, which were used within the Soviet supplied 9K33 Osa SAM regiment delivered between 1980 and 1985. On 7 December 1981, the delegation of the Polish Ministry of Internal Affairs went to the Soviet Ministry of Internal Affairs asking for equipment and supplies necessary to equip around 60,000 MO operatives and reservists enlisted because of the intensified activities against the Communist government. In response, on 17 December, the Soviet Ministry of Internal Affairs decided to transfer 25 BTR-60PBs along with 10,250,000 "Czeromucha" incapacitating chemical devices and 2,000 tonnes of gas over to its Polish counterpart. These vehicles had previously been used in Afghanistan. They were later modified by adding another radio set. They were used by ZOMO. During the martial law in Poland, the MSW automobile plant in Łódź fitted some BTRs with breakers mounted on the front of the vehicle, which were used for clearing obstacles (See Poland section in the Variants section for details). When the Milicja Obywatelska was transformed back into Policja in 1990, all BTR-60PBs had their armament removed. This was because Policja, unlike MO, didn't have a need for weaponry with such a high muzzle velocity – such weapons were dangerous to use in urban areas. The MO needed such weaponry because it was also supposed to carry out anti-partisan operations. Policja used unarmed BTR-60PBs for security during European Economy Summit 2004 in Warsaw, as well as for clearing blockades set up by the Samoobrona political party. A few Police BTR-60PBs are kept in storage for anti-riot duty as barricade breakers. People's Republic of China PRC reversed engineered the BTR-60PB after capturing four examples during the Sino-Soviet border conflict on Zhenbao Island in March 1969. The program was completed in the late 1970s. However, the vehicle did not enter service in large numbers because the PRC's primitive road system and rugged terrain meant that the wheeled APC was not well suited for the Chinese