Qatar has banned contractors from leaving the small, oil-rich country as it carries out a probe into how heavy rains damaged buildings and roadways. An article late Friday on the state-run Qatar News Agency announced the travel ban. It said “owners of companies, contractors and consulting engineers” would be banned from traveling abroad until the end of the probe. A year’s worth of rain on Wednesday deluged Doha’s Hamad International Airport, the home of Qatar Airways, pouring through at least one part of the roof. The airport cost at least $15 billion to build. Rainwater also flooded streets and shut down some stores in Doha.