Sales of existing homes in Maine plunged 30 percent in July compared to a year earlier, a drop blamed on the expiration of the federal homebuyer tax credit, according to statistics from the Maine Real Estate Information System Inc.

Median sales prices are still increasing, however. The median sales price rose 4.23 percent in July to $172,500, compared with July of 2009.

The volume drop in Maine reflected national trends, in which home sales declined 25.6 percent in July, according to the National Association of Realtors. Median prices rose less than 1 percent nationally, to $183,400 in July.

In the Northeast, median prices increased 4.8 percent to $263,800, while sales decreased 30.3 percent.

Marc Chadbourne, president of the Maine Association of Realtors, said the steep drops were anticipated in the industry.

“It was expected we’d see a decrease in sales in the third quarter, due to the wildly successful tax credits that buyers cashed in during the first half of 2010,” he said.