WASHINGTON (Reuters) - Ten additional states have joined the U.S. Justice Department's lawsuit against Live Nation-Ticketmaster for monopolizing markets across the live concert industry, the department said on Monday.

The Justice Department, along with a group of 30 states and the District of Columbia, filed the lawsuit in May to break up Live Nation [LYV.N], arguing the concert promoter and its Ticketmaster unit illegally inflated concert ticket prices and hurt artists.