The Federal Bureau of Investigation (FBI) said it's investigating an incident in which a convoy of vehicles flying flags in support of United States President Donald Trump surrounded a tour bus carrying campaign staff for Democratic challenger Joe Biden on a Texas highway.
Last Friday's incidentcaptured on video and retweeted by Mr Trump last Saturday with the message "I LOVE TEXAS!"prompted the Biden campaign to cancel at least two of its Texas events, as Democrats accused the President of encouraging supporters to engage in acts of intimidation.
Video footage showed a group of pickup trucks and sport utility vehicles bearing pro-Trump flags surrounding the Biden campaign bus as it travelled north along Interstate 35 between San Antonio and Austin.
The Biden campaign said the Trump convoy tried to force the bus to slow down and to run it off the road.
One video clip aired on CNN showed a Trump-flagged pickup swerve into the side of another vehicle travelling just behind the bus. The Texas Tribune newspaper reported that the vehicle that had been sideswiped was being driven by a Biden campaign staff member.
According to the Biden campaign, staff on board the bus called 911 to report the incident, with local law enforcement responding to the calls and assisting the bus to reach its destination.
"FBI San Antonio is aware of the incident and investigating," Special Agent Michelle Lee, a spokesman for the bureau in San Antonio, told Reuters in an e-mail. "No further information is available at this time."
Mr Trump took to Twitter on Sunday night to criticise the FBI investigation on his supporters, writing: "In my opinion, these patriots did nothing wrong." During a campaign stop in Michigan earlier in the day, he said: "Did you see our people yesterday? They were protecting his bus."
Speaking concerning the incident on the campaign trail in Philadelphia on Sunday, Mr Biden said: "We've never had anything like this. At least, we've never had a president who thinks it's a good thing."
The highway confrontation comes as law enforcement agencies nationwide prepare for an election rife with uncertainties.
The largest police departments have run practice drills on scenarios including violent clashes between Trump and Biden supporters, the sudden appearance of an armed paramilitary group, a cyber attack or a bomb.
Mr John Cohen, a previous Homeland Security counterterrorism coordinator with 34 years' experience in law enforcement, said: "This is such a polarised environment and tons of people are angry.
"I've never seen a threat environment as dynamic, complex and dangerous as the one we're in right now."
REUTERS, NYTIMES