BUENOS AIRES, Argentina (JTA) – A sophisticated test found no gunpowder on the hands of AMIA special prosecutor Alberto Nisman.

The release of the test results comes as dozens of cities in 28 countries have confirmed that they will hold rallies on Feb. 18 to mark the passing of one month since Nisman was found dead in his apartment.

The microscopic electron scanning test conducted Tuesday in a specialized laboratory in northern Argentina is the second test in search of a trace of gunpowder.

The test comes three weeks after Nisman’s unexplained death, hours before he was to present evidence to Argentine lawmakers that President Cristina Fernandez de Kirchner covered up Iran’s role in the 1994 attack on the AMIA Jewish center in Buenos Aires that left 85 dead and hundreds wounded.

Explanations range from suicide to an attempted operation against the government.

The new discovery seems to support the hypothesis that the prosecutor could have been murdered, though some experts explained on Wednesday on Argentinian news programs that the .22-calibre Bersa pistol that killed Nisman is a type of gun that sometimes does not leave traces of gunpowder.

In an interview published Tuesday in the Washington Post, Argentinian Foreign Minister Hector Timerman defended the Memorandum of Understanding signed by Argentina and Iran to investigate the Islamic Republic’s involvement in the AMIA bombing. Timerman said that his government does not gain anything with Nisman´s death and revealed that the United States did not want to push the AMIA issue in negotiations with Iran

Timerman told the Post that he asked the Argentine ambassador to Washington to send a letter to U.S> Secretary of State John Kerry “asking that they include the AMIA case in their negotiations with the Iranians. They told us that it was not possible.”

Meanwhile, The AMIA Jewish center confirmed that the institution will participate in the rally for justice organized by the judicial employees union and prosecutors in memory of Nisman, to be held on Feb. 18, exactly one month after the AMIA prosecutor was found dead.

Quickly, the list of cities around the world in which will mark the one-month anniversary of the unexplained death is growing and currently stands at 28 countries.

In the United States, cities that will hold rallies include Miami Beach, New York, Chicago, Los Angeles, Washington D.C., Minneapolis, Las Vegas, Houston and San Francisco.

Other cities world-wideto hold rallies include Paris, Athens, Toronto, Montreal, Sidney, Berlin, Frankfurt, Vienna. Santiago, Bogota, Rome, Milan, Tokyo, Oslo, Lima. Caracas and Bern.