By TMZ

Retired former five division world champion Floyd Mayweather Jr. had one of his entourage's vans burnt to a crisp in what appears to be an arson attack this weekend in the UK.

Floyd was speaking at an event inside the International Convention Centre in Birmingham Saturday night when 1 of his custom TMT vans was torched outside and left smoldering.

The boxer is currently on his "Undefeated" tour, where he's speaking in front of audiences and doing meet-and-greets with fans.

We've reached out to local authorities ... who issued the following.

 A rep for the Ladywood Fire Station -- which responded to the fire -- tells TMZ that 2 individuals chucked a Molotov cocktail inside after breaking a window with a brick. We're told the van was connected to Floyd's entourage and the team handling his promotions while he's in the UK. Sources close to Floyd tell us the van was not actually owned by him. The case has been passed off to cops.

There's a silver lining for Floyd here -- he lost just 1 van ... as opposed to 4 expensive cars like the last time this happened.