Venezuelan police announced six arrests on Sunday with the promise of more to come following an alleged assassination attempt against President Nicolas Maduro using explosive-laden drones.

Maduro ally President Evo Morales of Bolivia accused the U.S. government of masterminding the plot, a charge swiftly denied by Secretary of State Mike Pompeo and National Security Adviser John Bolton.

Maduro was delivering a televised speech on Saturday evening at an event commemorating the 81st anniversary of the Venezuelan National Guard (which currently operates more like a militia directly commanded by the Venezuelan president than what Americans think of as a “national guard” force) when a loud explosion caused the troops to flee in panic.

The embarrassing rout of the National Guard, which reportedly threw civilians out of its way to reach safety, has been cited by observers as a reason to doubt Maduro arranged the explosion himself as a false-flag operation to solidify his political support and justify a new crackdown on the opposition.

“Seeing trained soldiers fleeing in apparent panic and disarray before an explosion strongly contrasts with the idea of monolithic control and loyalty of security forces that Maduro prides himself on,” the Torino Capital Investment Firm of New York pointed out to the Associated Press.

Venezuelan firefighters initially said the explosion was caused by a gas tank detonating in a nearby apartment building, but Maduro’s regime quickly advanced a story about unknown terrorists trying to eliminate Maduro and decapitate his government with bomb drones, as the AP reported:

Defense Minister Vladimir Padrino Lopez, appearing on state television Sunday, said the attackers were trying to wipe out Venezuela’s entire top leadership along with Maduro. Interior Minister Nestor Reverol said two drones, each packed with a kilogram (2.2 pounds) of C-4 plastic explosive, were flown toward Maduro, his wife and other top leaders as the president spoke to hundreds of troops during an event celebrating the 81st anniversary of the National Guard. One of the drones was intended to explode above Maduro and the other was to detonate directly in front of him, Reverol said. The military managed to knock one of the drones off course electronically and the other craft crashed into an apartment building two blocks away, Reverol said. “We have six terrorists and assassins detained,” he said. “In the next hours, there could be more arrests.” Reverol said two of those arrested had previous run-ins with the government, although he did not give their names. He said one took part in the 2014 anti-government protests that rocked Venezuela’s as it descended deeper into an economic crisis that is now worse than the Great Depression. The other had a warrant out for his arrest for participating in an attack on a military barracks, the interior minister said.

Maduro himself claimed to see a “flying device” explode and said he initially thought it was a detonation of celebratory fireworks. He said he heard a second explosion moments later. The live television broadcast of the event captured Maduro and his wife looking up at something in surprise when the first detonation occurred.

Associated Press reporters said a witness showed them cell-phone video of a drone, but their description of the clip did not sound conclusive. If the incident on Saturday evening was indeed an attack on Maduro using bomb-laden drones, it would mark the first confirmed use of drones to assassinate a head of state.

Information Minister Jorge Rodriguez advanced a theory that “far right” opponents of Maduro’s rule worked with hostile forces based in Miami and Bogota to plan the attack.

“The investigation will get to the bottom of this, no matter who falls,” he vowed.

“The name of Juan Manuel Santos is behind this attack. The first elements of our investigation point to Bogota,” Maduro himself declared, referring to the president of Colombia.

The Columbian government “emphatically rejected” these accusations in a weekend statement and called them “absurd.” The statement noted that Maduro’s government has a penchant for blaming its misfortunes on interference from Colombia. In fact, the speech Maduro delivered to the National Guard ceremony on Saturday night included a few potshots at the “oligarchs in Bogota.”

Bolivian President Evo Morales, a staunch ally of Maduro, went further on Sunday and blamed the Trump administration for masterminding the attack in an act of “Yankee interventionism.”

National Security Adviser John Bolton rejected these charges in a “Fox News Sunday” appearance.

“I can say unequivocally there was no U.S. government involvement in this at all,” said Bolton.

“If the government of Venezuela has hard information that they want to present to us that would show a potential violation of U.S. criminal law, we’ll take a serious look at it, but in the meantime, I think what we really should focus on is the corruption and oppression in the Maduro regime in Venezuela,” he added.

Secretary of State Mike Pompeo seconded Bolton’s comments on Sunday night while on his way back to Washington from the Association of Southeast Asian Nations.

“Ambassador Bolton said this morning there wasn’t an American connection. We don’t really have a lot of detail about what took place beyond what you’ve seen and what the — I think the White House has put out so far,” said Pompeo.

There has been one claim of responsibility for the attack so far, made by a previously obscure group called “Soldiers in T-shirts.” The group stated that it tried to attack Maduro with two explosive-laden drones but the vehicles were shot down by government troops.

“It was not successful today, but it is just a matter of time,” the group said through its Twitter account.

Opposition groups said this statement read suspiciously like something the Maduro regime would invent if the attack was a false-flag operation, or if it was a real attack but the government was eager to use it as an excuse for a broad crackdown on political opponents.

“It’s evident that the initial reaction of the government isn’t aimed at attempting to clarify what happened but rather to take advantage of the situation and irresponsibly and sweepingly attack the ‘opposition,’” a group called the Broad Front said in a statement.

The other likely suspect for a genuine attack would be the group of renegade soldiers formerly headed by colorful ex-police officer and action movie star Oscar Perez, killed in January during a gun battle with police six months after he flew a hijacked helicopter in a grenade attack on Venezuelan government buildings. If the claim of responsibility from “Soldiers in T-shirts” is authentic, it is unclear whether they have some relationship with Perez and his operation.

Venezuelan activists in Miami are worried that Maduro will use the attack as an excuse for further oppression.

“We believe that the regime will launch a fierce attack against the opposition, there will be more violations of human rights, and this gives rise to arrest, accuse and persecute the opposition within the country,” former National Guard officer Jose Antonio Colina, president of Politically Persecuted Venezuelans in Exile, said on Sunday.