A Minnesota man with suspected ties to white supremacist groups had devised a plan to attack the Mexican consulate in St. Paul and believed his actions would "manifest national awareness," according to a federal affidavit obtained Thursday by The Associated Press.

The affidavit, recently unsealed in federal court, provides details of the investigation into the alleged plans of Joseph Benjamin Thomas. The 42-year-old was indicted in April on drug charges, though authorities were investigating him and another man as part of a domestic terrorism probe.

Investigators claimed the men had amassed weapons and hundreds of rounds of ammunition as part of a plan to attack the government, minorities and others.

Thomas is not facing any terrorism-related charges. A message left for Thomas' attorney was not immediately returned Thursday, and the U.S. Attorney's Office declined to comment on the case.

The FBI affidavit alleges Thomas told an undercover agent he was plotting to steal a pickup truck, load it with barrels of oil and gas, drive it into the consulate and allow the mixture to spill. The mixture would then be set ablaze with a road flare.

The affidavit said Thomas originally wanted to carry out the attack the eve of May 1, a day that in recent years has been used by activists in the U.S. to hold rallies for immigrant rights. But Thomas later said the attack could not happen on that day because of "personal factors complicating his life," the FBI affidavit said.

Agents saw Thomas conducting surveillance on the consulate building in December. At that point, he told an undercover agent he wasn't sure if the plot should move forward, but he continued to develop it and found a place where 55-gallon barrels could be stolen for use in the attack, the document alleges.

Thomas also told an undercover agent that he had books containing recipes for a mixture to fill the barrels, and he had found instructions for producing napalm, the affidavit said.

"We consider him a threat, and we believe he had the capacity to carry these threats out," FBI spokesman Kyle Loven said in an interview Thursday. "This was a lengthy investigation, and it was driven by our belief that the intentions of these persons were sincere."

Ana Fajer, the consul of Mexico based in St. Paul, said the consulate hadn't received any threats and didn't know about Thomas' plan until it came up in court.

Thomas, from the St. Paul suburb of Mendota Heights, and another man, 31-year-old Samuel James Johnson of Austin, Minn., were arrested last month. According to an affidavit unsealed at the time of their arrests, the two had been amassing weapons and ammunition with plans to target government, minorities and others.

Johnson was indicted on weapons charges. The indictment said he has prior convictions for armed crimes and was not allowed to have weapons, but from late 2010 through late last year, he was found with five weapons - including a semi-automatic assault rifle - and more than 1,000 rounds of ammunition.

Thomas was indicted on four charges related to possession and sale of methamphetamine.

According to the earlier affidavit, Johnson was a former member and Minnesota leader of the National Socialist Movement, a white nationalist group, and he and Thomas were trying to form a spinoff group called the Aryan Liberation Movement.

With the new group, Johnson planned to "recruit and train other white supremacist sympathizers toward a final goal of committing acts of violence against the United States government and minority individuals," the affidavit said.