NEW YORK (CNN/Money) - ImClone Systems Inc. posted a sharply wider first-quarter net loss Thursday, falling far short of Wall Street estimates on a drop in sales.

For the quarter ended March 31, the drugmaker, whose marketing of cancer treatment Erbitux is being investigated by federal authorities, reported a net loss of $30 million, or 41 cents a share, far wider than the net loss of $1.2 million, or 2 cents a share, a year earlier. Analysts polled by earnings tracker First Call expected a loss of 34 cents a share.

Sales fell to $18.6 million from $28 million.

The New York-based company also said expenses jumped to $48.2 million from $28.8 million a year ago, including fees related to a marketing agreement on Erbitux.

ImClone's (IMCL: Research, Estimates) shares slid $2.73 in before-hours trading Thursday on Instinent.