Beitbridge - Zimbabwean authorities have said that they are investigating a "third force" after a recent violent protest rocked the Beitbridge border, a report said on Monday. According to the state-owned Herald newspaper, State Security Minister Kembo Mohadi expressed concerns over the "violence" that had engulfed the protest on Friday. Mohadi further claimed that the ringleaders of the protests were seen wearing T-shirts that had become "familiar" at opposition party demonstrations.He said Zimbabwean nationals were not usually violent people when they held demonstrations, thus, the government was shocked by the violence. "The way they carried out the operations is unlike Zimbabweans. Our people are known for holding peaceful demonstrations, rather than vandalising or burning tyres," Mohadi was quoted as saying.Reports indicated that properties and vehicles worth thousands of dollars were burnt by angry protesters at the Zimbabwean-South African border gate.The protest came after Zimbabwean authorities limited imports of a vast range of goods, including beauty products.Zimbabwean retailers were no longer allowed to freely bring jam, mayonnaise, wardrobes and wheelbarrows, among other things, into the country.At least 71 people were arrested over the protests. Meanwhile, the main opposition Movement for Democratic Change (MDC), led by Morgan Tsvangirai, expressed concern over the "disturbances" at the border. In a statement sent to News24, MDC spokesperson Obert Gutu took a swipe at President Robert Mugabe's government for banning imports of basic commodities. Gutu said that his party was on the side of the poor, thus, they were "deeply" concerned over the importation ban. "The Zanu-PF regime bungled in a very big way when it imposed the ban on the importation of basic goods and commodities. It is a notorious fact that more than 85% of Zimbabweans survive within the informal sector largely because industries and factories have since been closed following upon decades of Zanu-PF misrule, unprecedented corruption and rampant mismanagement of the economy," said Gutu.