Fans crowded the streets outside the Staples Center in Los Angeles after the Lakers beat the Miami Heat 106-93 to win the NBA Finals in six games.
Anthony Davis had 19 points and 15 rebounds for the Lakers, which was still coming to terms with the death of iconic former Lakers star Kobe Bryant in January.
Players also faced the challenges that came with leaving home for three months to play in a bubble designed to keep inhabitants safe from the coronavirus.
The league’s "bubble chapter" was put together after a four-and-a-half-month suspension of play that from March 11 because of the coronavirus pandemic.
Celebrations were mostly peaceful but some rocks and bottles were thrown at officers. Videos posted online also showed cars doing "doughnuts" and fireworks being set off in the street, which is illegal in the state without a permit.
Witnesses told the Los Angeles Times that officers fired “beanbag rounds” at one point, which sent some people running.
A few officers on horseback worked to push the crowd away from Staples Center, where the Lakers usually play.
Later in the night, the large gathering fractured into several groups, and some people were detained.
Los Angeles Mayor Eric Garcetti discouraged public gatherings to celebrate the win, instead urging fans to cheer on the team from home.
“As we cheer our Lakers' 17th championship, please remember it’s still not safe to gather in groups,” the mayor tweeted, in reference to the coronavirus pandemic.