CINCINNATI (AP) — Kroger Co. says that sales at established stores fell for the second straight quarter after more than seven years of consecutive growth, signaling that competition for the supermarket is growing more intense.

The Cincinnati grocer cut its profit outlook, sending shares plunging 10 percent before the opening bell.

There is heightened competition in the grocery industry, with German discounters Aldi and Lidl attempting to draw more shoppers through low prices. For the quarter, Kroger said sales at established supermarkets fell 0.2 percent for the three months ended May 20. That follows a 0.7 percent decline in the previous quarter.

Kroger CEO Rodney McMullen said the company is focusing on its strategy for lowering its own costs so that it can keep prices affordable for shoppers.

For the quarter, the company earned $303 million, or 32 cents per share. Earnings, adjusted for non-recurring costs, came to 58 cents per share, which was a penny more than analysts expected, according to Zacks Investment Research.

Total revenue was $36.28 billion, higher than the $35.51 billion Wall Street expected.

Kroger expects full-year earnings in the range of $2 to $2.05 per share, down from its previous guidance of $2.21 to $2.25 per share. Its stock was down more than 9 percent at $27.39 in morning trading.