The state Department of Environmental Protection has searched a former industrial diamond abrasives factory in Verona to find out what happened to more than two gallons of a highly toxic mixture containing the metallic element thallium, also known as the poisoner's poison.

DEP investigators obtained a search warrant for the former Industrial Diamond Powders Inc. building on Sandy Creek Road and searched on Thursday for a stainless steel container holding the thallium liquid mixture. The solution is used to separate diamond fragments and minerals in the abrasives reprocessing operation that closed at the end of 2003.

Helen Humphreys, a DEP spokeswoman, confirmed that the factory building was searched by agents with the department's office of Chief Counsel but declined to say if anything was found.

"We haven't reached any conclusion yet," she said. "We are concerned. The allegations are serious and we are conducting an investigation based on those allegations."

About 330,000 grams -- or 2.5 gallons -- of the thallium solution was in the factory when it was sold, according to Fred Pena, who told the DEP about the missing thallium. He was Industrial Diamond Powder's plant manager. He placed the value of the solution at $1.78 million.

Mr. Pena's father, Fred Pena Sr., owned the abrasives company until his death in July 2003.

Mr. Pena also reported the lost thallium to the FBI and the Department of Homeland Security. The FBI would neither confirm nor deny any investigation.

Disposal of the thallium and thallium compounds, which was used for 50 years by the company, is regulated by the DEP because it is highly toxic and poisonous. It is a suspected carcinogen and can enter the body through skin contact, either as a gas or liquid. It is a slow-acting poison that causes hair loss, flu-like symptoms, excruciating skin and joint pain, paralysis and within two weeks, respiratory failure.

It was reportedly employed by former Iraqi dictator Saddam Hussein and has often been used by mystery book writers to kill off victims. Thallium's toxicity also led to its use as a rat and ant poison, but because it is considered too dangerous, most countries, including the U.S., have banned its use in that manner.

Also in the building, according to Mr. Pena, were other materials used in the abrasives production process, including semi-precious metals cobalt, tungsten and tantalum, and more than 300,000 carats of industrial diamond powder.

The diamond abrasives company closed at the end of 2003 and the factory site was sold "as is" for $50,000 in March 2006 by Mahady & Mahady, a Greensburg law firm that was the court-appointed executor of his father's estate.

Mr. Pena, who was the original executor of his father's estate before a family dispute resulted in the appointment of Mahady & Mahady, has claimed in a petition that the law firm mishandled the property by allowing its sale below appraised value and in violation of state environmental disposal regulations.

Mr. Pena earlier this month filed a petition asking Westmoreland County Common Pleas Court to remove the law firm as administrator of his father's estate.

He said a Jan. 19, 2006, letter from the law firm to heirs of his father's estate said estate's administrator had agreed to accept the $50,000 "as is" offer because there were no others and "the administrator and the realtors have serious questions about environmental issues on the property."

George A. Butler, the Mahady & Mahady attorney who sent that letter, said in a phone interview last week that he knew nothing about any thallium in the factory when it was sold.

"I had no idea. The estate was sold a couple of years ago and sold 'as is.' I didn't know anything about any thallium," Mr. Butler said. "The environmental issues I was referring to [in the letter] were unknown. We didn't know what was there or what had been done there in past years."

Mr. Pena said he did inventories that listed the thallium and discussed the need to safely dispose of it in multiple meetings with the law firm.

"I warned them before they sold it about the thallium and focused on the danger," Mr. Pena said. "I warned the new owner too, to stay away from it."

The former factory is now being used by a home building and remodeling company. Officials there could not be reached for comment.