According to sources familiar with the situation, Russia planned to send incendiary devices via a commercial carrier on planes that would potentially arrive in the United States.

Four people have been charged in Poland over camouflaged explosives that “detonated during road and air transport” in the UK in July, according to a statement from the country’s prosecutor’s office.

In the statement made by the Polish prosecutor’s office, “The activities of the group consisted of sabotage and diversion related to the sending of packages containing camouflaged explosives and dangerous substances that spontaneously ignite or explode during land and air transportation to the European Union countries and Great Britain through courier companies.” The statement was included. .

“The group’s goal was also to test the transfer channel for such packages that would ultimately be destined for the United States and Canada,” according to the statement.

“I’m not sure Russia’s political leaders are aware of the consequences if one of these packages explodes and causes mass casualty,” Pawel Szota, the head of the foreign intelligence agency, told The Wall Street Journal. story.

ABC News has reached out to Szota for comment.

The UK Metropolitan Police also confirmed that officers from its counter-terrorism unit were investigating the incident, which took place in Birmingham, England.

“On Monday 22 July, a parcel caught fire in the area. It was attended to by staff and local fire crews at the time and there were no reports of any injuries or serious damage,” the Met said in a statement. he said.

No arrests were made in the incident.

The Transportation Security Administration remains alert to threats to aviation and air cargo systems and there is no active threat targeting U.S.-bound flights, a U.S. official told ABC News.

The incident in England and another incident in Germany are believed to be part of a wider conspiracy, according to a source familiar with the investigation.

A senior US counterterrorism official confirmed to ABC News that the US was warned about Russian efforts over the summer. European officials told their American counterparts that they believed the Russians were trying to send incendiary devices that would explode inside locations supporting Ukraine’s war effort to prevent Ukraine from continuing to fight the Russian occupation.

European officials do not believe the Russians were planning or trying to shoot down a commercial or cargo plane, the official said. However, the devices do not always work properly, and the risks to commercial and civil aviation are serious when incendiary devices are activated and transported.

TSA did not address the incidents abroad but told ABC News in a statement that the agency was “constantly adjusting its posture” and promptly shared all relevant information.

“Over the past several months, as part of a multi-layered security approach, TSA has worked with industry partners to put in place additional security measures for U.S. aircraft operators and foreign air carriers regarding certain cargo shipments to the United States in accordance with 2021,” the statement said. TSA Air Cargo Security Roadmap.” “We greatly appreciate the collaboration and cooperation with the industry as we work together to ensure the safety and security of air cargo.”