CNN  —  Rising gas prices and stubbornly high shelter costs have stalled some of the progress made on slowing inflation. US consumer prices picked up again last month, marking a 3.5% increase for the 12 months ended in March, according to the latest Consumer Price Index data released Wednesday by the Bureau of Labor Statistics. That jumps from February’s 3.2% rate and marks the highest annual gain in the past six months, highlighting how the path to lower inflation remains bumpy. On a monthly basis, prices were unchanged from February’s 0.4% gain. Economists were expecting a 0.3% monthly increase and an annual rate of 3.4%, according to FactSet consensus estimates.