Melbourne underworld identity Mick Gatto is being questioned by police over an assault.
The alleged offence happened on Tuesday at Gatto's business Elite Cranes in Brooklyn in the city's west.
Victorian police said Gatto was taken to Altona North police station for questioning on Wednesday.
In 2005, Gatto was acquitted of murder charges over the 2004 shooting death of underworld hitman Andrew Veniamin on self defence grounds.