Inflation accelerated in May, reaching its highest level in three years.

The Consumer Price Index increased 4.2% from a year earlier, up from 3.8% in April, according to new data from the Bureau of Labor Statistics.

Consumer prices rose 0.5% during the month. Economists surveyed by FactSet and Dow Jones had expected the annual inflation rate to reach 4.2%.

Reports said higher energy costs helped push inflation higher in May.

Excluding food and energy prices, core inflation rose 0.2% during the month and was up 2.9% from a year ago.