Four Red Cross officials have arrived in Cuba to visit political prisoners and investigate prison conditions for the first time since Fidel Castro came to power 29 years ago, an organization spokesman said Tuesday. Carlos Bauverd, spokesman for the Geneva-based International Committee of the Red Cross, said the team arrived in Havana on Monday and hoped to begin visiting prisoners Tuesday. Cuba is believed to be the third Soviet ally to permit the Red Cross to visit prisoners. Poland and Afghanistan have already done so. The officials, including one doctor, hoped to visit every political prisoner in the Communist country during their monthlong stay.