Shares of wireless technology developer InterDigital Inc. fell Monday after the International Trade Commission rejected the company's claim that Nokia Corp. phones infringe on InterDigital's patents.

The King of Prussia, Pa.-based company's stock fell $4.44, or 18 percent, to $20 in afternoon trading on heavy volume.

The commission made an initial determination in the case in August, finding that Nokia did not infringe on four InterDigital patents. InterDigital said late Friday that the ITC has now confirmed that finding, ending its investigation.

InterDigital CEO William J. Merritt said the company remains confident in achieving its goal of getting all makers of 3G phones to sign license agreements.