Nairobi - A US-based campaign data company confirmed on Saturday that its CEO was detained in Kenya and faced deportation after working on the opposition's campaign ahead of Tuesday's tightly contested presidential election.The detention of the CEO of Aristotle, Incorporated raised further concerns about the upcoming vote just days after a top Kenyan election official responsible for the electronic voting system was found tortured and killed.Brandi Travis with Aristotle said CEO John Aristotle Phillips, an American, and Canadian staffer Andreas Katsouris were detained Friday night and faced deportation later Saturday. Travis said Phillips was at the US Embassy in Nairobi.The two men were assisting opposition candidate Raila Odinga with issues including strategy and data analysis and had chosen to get involved in the Kenyan election because they thought it had the potential for irregularities, Travis told The Associated Press."We pick our international campaigns very carefully," Travis said. "Odinga was a candidate they really believed in."Post-election violence Both Odinga and Kenyan President Uhuru Kenyatta were in their final day of campaigning Saturday as some in the East African nation worried that the vote could turn violent, as it did a decade ago. Kenyatta is the son of Kenya's first president; Odinga is the son of the country's first vice president and has run in vain for the top post in three previous contests.Recent elections in the east African high-tech and commercial hub have been hotly contested, and more than 1 000 people were killed in post-election violence in 2007. Kenyatta prevailed over Odinga in a 2013 vote that was mostly peaceful but tainted by opposition allegations of vote-rigging. Former US Secretary of State John Kerry is among the thousands of expected election observers this time around.Some in the nation of 44 million people have been leaving the capital because of the threat of chaos, while many are simply going home to vote.The torture and killing in recent days of an election official, Christopher Msando, in charge of the electronic voting system has some concerned about the possibility of vote tampering. No arrests have been reported.On Saturday, Kenya's main opposition party said the American and Canadian who were assisting its campaign were taken from their homes on Friday. It was not immediately clear why they were detained.'Thrown into the boot'James Orengo, a senior member of the opposition National Super Alliance, identified the American as Phillips.Orengo told reporters that Phillips was "very adamant about his rights under the constitution, civic rights, was molested, thrown into the boot, and taken away with his colleague".The US Embassy in Kenya said on Twitter that the American and Canadian, without identifying them, were "safe and departing" the country. The embassy said US and Canadian officials had been in touch with their detained citizens as well as the Kenyan government.The detentions occurred at around the same time that armed and masked police raided an opposition vote counting center, intimidating workers and seizing equipment, Orengo said. He also said two Ghanaians working on the opposition campaign have been deported.Kenyan police denied allegations that officers broke into political party offices on Friday, saying no report of a burglary has been made to any police station.