WASHINGTON—Unemployment rates rose in 28 U.S. states last month, partly because more Americans started looking for work and not all of them found jobs.

Unemployment rates fell in 11 states and were unchanged in another 11, the Labor Department said Thursday.

Nationwide, hiring has picked up this year, but the unemployment rate rose in May to 7.6 percent from 7.5 percent in April and stayed the same last month. That's because more people began job searches in May and June but not all of them found work. The government doesn't count people as unemployed unless they are actively searching for work.

A similar dynamic occurred at the state level. Two-thirds of the states added jobs in June. Massachusetts, Maryland and Georgia were among the states where the unemployment rate rose even though they added jobs.

Massachusetts also reported the largest unemployment rate increase for any state. It rose to 7 percent in June from 6.6 percent in May. Georgia, Maryland and Vermont reported increases of 0.3 percentage points, the next largest gains.

Alabama's unemployment rate fell to 6.5 percent from 6.8 percent, the biggest decline among the states. Wisconsin reported the next biggest drop, to 6.8 percent from 7 percent.

California added 30,200 jobs in June, the most of any state, followed by Pennsylvania, with 19,100, and Wisconsin, at 17,500. Tennessee lost 16,500, the most of any state, followed by Ohio, with a loss of 12,500, and New York, which lost 11,400.

Nevada's unemployment rate of 9.6 percent was the highest in the nation, followed by Illinois at 9.2 percent and Mississippi at 9 percent. North Dakota's 3.1 percent rate was the lowest.

Economists hope that better hiring nationwide will accelerate growth in the second half of this year. Employers added an average of 202,000 jobs per month in the first six months of this year, up from 180,000 in the previous six months.