Three American diplomats were briefly detained in Russia near the military test site where a mysterious explosion released radiation in August, several Russia state news agencies have reported.

The US embassy has confirmed the incident, the Interfax news service reported, but said the three diplomats had filed the proper paperwork to travel in the area.

The Russian foreign ministry said the diplomats had named a different city as their destination and had “obviously got lost”.

The report comes just days after the United States said the accident was caused by a nuclear reaction when Russia tried to retrieve a nuclear-powered cruise missile from the Barents Sea.

The diplomats were detained on Monday on a train in the city of Severodvinsk, near where Russian authorities said they had been testing a rocket engine with a nuclear component before the accident took place.

The diplomats, who have been identified by Interfax as military attaches, were later released, but could face administrative charges for traveling in a restricted military area, agencies reported.

In a statement, the Russian foreign ministry confirmed that the diplomats were on an official trip and had informed the Russian defence ministry of their plans.

“Only, they said their intention was to visit Arkhangelsk and they ended up en route to Severodvinsk,” the ministry said.

“They obviously got lost. We are ready to give the US embassy a map of Russia,” the ministry added.

The blast at the military test site in August killed at least five people and caused panic after radiation levels jumped to 16 times their normal levels in nearby Severodvinsk.

Russian authorities have given little information about the accident. But a US diplomat this week said that the accident took place when Russia attempted to retrieve a nuclear-powered cruise missile called Burevestnik from the Barents Sea.

“The United States has determined that the explosion near Nyonoksa was the result of a nuclear reaction that occurred during the recovery of a Russian nuclear-powered cruise missile,” Thomas DiNanno, the diplomat, said during a speech at the UN.

Russia’s plans for a nuclear-powered cruise missile that could in theory fly indefinitely were first revealed by Vladimir Putin during a speech last year. The missile is still undergoing testing, and some weapons experts doubt if it can ever be made operable.

Russia’s military was attempting to retrieve the missile from another failed 2017 test when the accident took place.

It was not immediately clear whether the diplomats were traveling to or from Nyonoksa, the village near the military testing site, when they were detained. But train timetables would indicate they were returning from the village when they were arrested close to 6pm in Severodvinsk.

Russia has maintained a shroud of secrecy around the incident, closing off waters in the White Sea to foreign ships to prevent them from collecting information about the explosion.