Walgreen Co has recorded a 16 per cent rise in earnings during the third quarter of the year but investors expressed concerns over the low growth in sectors besides the company's pharmacies.

Walgreen, which is based in Deerfield, recorded lower than expected results as its earnings grew mainly because of the low base in the previous year when the company was slit. Walgreen's gross margin, which is a basic measure of profitability, grew at a low face surprising many market analysts. They said that the nation's largest drugstore operator might be losing momentum that was gathered in the generic business.

The availability of generic medications had helped the company increase its earnings as they offer wider margin between the cost for the pharmacy for acquiring the drugs and the selling price. Generic products entered with the conclusion of patent rights of pharmaceutical giants in the US and other countries.

The shares of Walgreen fell 6.1 per cent or $2.93, to $45.12 Tuesday afternoon. The shares of the company had risen 30 per cent so far this year before the fall on Tuesday.