Munich International Airport in Munich, on July 6, 2019. (Wikimedia Commons)

European security officials have linked suspected Russian agents to a plot to smuggle incendiary devices onto a cargo plane in Germany, in what investigators believe may have been a test for future attacks on planes bound for North America.

An international investigation that began after one of the devices caught fire prematurely in July determined that the conspirators also sent packages without the flammable contents to addresses in the United States and Canada, in an apparent test to see if the packages could be successfully delivered. according to European security. officials.

The plan to set fires on board planes was being seen as a provocative and particularly dangerous escalation in an alleged sabotage campaign led by Moscow against NATO countries helping Ukraine defend itself against a Russian military invasion. Russia has denied any connection to such plots.

The new revelations come 10 days after Poland’s National Prosecutor’s Office announced the arrest of four people as part of an ongoing investigation. in “foreign intelligence activities through acts of sabotage” in Poland and other European Union member states, according to a statement. Arrest warrants were issued for two other people who are still at large.

The suspects were accused of sending packages containing “disguised explosives and hazardous materials” using international courier services, the prosecutor said.

“The group’s goal was also to test the transfer channel for such packages, which would ultimately be sent to the United States of America and Canada,” the statement read.

Three European security officials confirmed that the packages had been linked to a sabotage plot involving suspected Russian agents or their representatives. The officials, who spoke on condition of anonymity to discuss an active investigation, said it was unclear whether the plot was directed by the Kremlin or lower-level intelligence officials.

One of the European officials said the plot appeared to be in its early stages and was relatively unsophisticated. The Wall Street Journal first reported new details of the investigation on Monday.

German authorities were initially alerted to the plot when a fire broke out at a cargo center in Leipzig, Germany, operated by the German-based international courier company DHL. The origin of the fire was due to a package containing an electronic massager that had been altered with the addition of a highly flammable form of magnesium.

The package came from Lithuania and caught fire during a stopover. It was marked for delivery to a false address in Birmingham, England, according to a German security official.

Fortunately, the package “ignited on the ground and not during a flight, avoiding what could have been a catastrophic situation,” the official said. “If it had exploded in the air, it could have caused an accident, and the debris could have injured people on the ground.”

According to a second European official familiar with the investigation, the same sender sent packages to addresses in the United States and Canada, without the flammable contents.

“The sender considered these packages to be evidence and wanted to see how far they could go,” the official said.

Biden administration officials refuse to address the details of the alleged bombing attempt. A senior U.S. official said there are “no current active threats involving flights bound for the United States.”

A spokesperson for the U.S. Transportation Security Administration said in a statement that the agency had implemented additional security measures to prevent sabotage involving cargo shipments bound for the United States.

“We continually adjust our security posture as appropriate and promptly share all relevant information with our industry partners, to include requirements and recommendations to help them reduce risk,” the spokesperson said.

Russian officials could not be reached for comment on Monday. Kremlin spokesman Dmitry Peskov previously told the Washington Post that accusations of Russian sabotage activity “were nothing more than a stoking of Russophobic hysteria.”

Greg Miller, Ellen Francis and Ian Duncan contributed to this report.