A Prince George's County man convicted in an extortion scheme was charged yesterday with possessing two weaponized toxic substances and at least eight hand grenades, federal authorities said.

Myron Tereshchuk, 42, was charged with possessing weaponized ricin and nicotine sulfate and other crimes in a six-count indictment returned by a federal grand jury in Maryland. He could be sentenced to life in prison if convicted, prosecutors said.

The FBI said in court filings that agents investigating a $17 million extortion plot that Tereshchuk directed against a business competitor discovered the prohibited substances in March during a search of his home on Queens Chapel Road in the Hyattsville area. The indictment alleges that he was not properly registered to possess ricin or hand grenades.

Neither the indictment in Baltimore nor records in federal court in Virginia, where Tereshchuk pleaded guilty in the extortion case, suggest any link to terrorism. The documents also do not specify how the toxins allegedly were weaponized.

Marcia Murphy, a spokeswoman for Maryland U.S. Attorney Thomas M. DiBiagio, declined to say how Tereshchuk allegedly planned to use the toxins or whether investigators suspect that he is connected to a terrorist group.

Michael Nachmanoff, the federal public defender who represented Tereshchuk in the Virginia case, did not return a call seeking comment yesterday afternoon. Tereshchuk's home number is unlisted.

The indictment does not say how much ricin or nicotine sulfate, a chemical used in pesticides, Tereshchuk allegedly possessed. It says he had "8 or more" hand grenades.

In Virginia, Tereshchuk pleaded guilty to attempted extortion in June. He remains in custody and is scheduled to be sentenced in connection with that case Oct. 22.

Court documents say that, starting in February 2003, Tereshchuk harassed the Connecticut-based company MicroPatent, a consulting firm that produces patent and trademark information. Prosecutors said Tereshchuk has a small business in the same field, Potomac Filewrapper Service.

The harassment culminated in the extortion demand one year later, with Tereshchuk threatening to disseminate the proprietary information he obtained by digging through the company's trash and other means. Tereshchuk used the alias "Bryan Ryan" in the extortion scheme, court records show, and he directed that the payments be in the form of checks made payable to Tereshchuk and delivered to his parents' house in Maryland.

In one e-mail, he wrote: "Stop stalling and mail Myron the checks NOW."

The Connecticut-based firm, which also has offices in Alexandria, contacted the authorities.

FBI agents searching Tereshchuk's home March 10 found firecrackers, chemicals, recipes for ricin and a postcard with the message "Here is your poison -- enjoy," according to documents filed in the Virginia court.