Green Mountain Coffee Roasters Inc., maker of Keurig single-cup capsules and brewers, has recently lowered coffee prices in some grocery stores, according to data released today from SymphonyIRI Group.

Green Mountain single-cup coffee was 1.1 percent less expensive in the four weeks ended June 10 at food, drug and mass retailers excluding Wal-Mart Stores Inc., compared with a year earlier, data from the Chicago-based researcher show. Packaged coffee prices for the overall category were up 4.9 percent in the four-week period.

The company is facing increased competition from private- label brands entering the single-cup coffee category as the main patents for its K-Cups expire in September. Kroger Co., the biggest U.S. grocery chain, said earlier this month that it’s planning to sell its own version of the pods used in Green Mountain’s Keurig brewers.

“Green Mountain is still a premium-priced product,” Kenneth Shea, senior consumer products analyst with Bloomberg Industries, said in an interview. “They have to keep pricing level or down if they’re going to fight this private-label threat.”

The shares fell 6.7 percent to $20.04 at 12:57 p.m. in New York. Waterbury, Vermont-based Green Mountain had tumbled 52 percent this year through yesterday.

Green Mountain single-cup coffee cost $7.89 a unit, on average, whereas private-label brands were $5.43 and all coffee was $6.86 during the four-week period, the data show. Starbucks Corp. ground-coffee prices, at $8.97 a unit, were also lower at food, drug and mass retailers compared with last year.

Suzanne DuLong, a Green Mountain spokeswoman, didn’t immediately respond to a telephone message and e-mail seeking comment.