The ref tried to continue the match after police temporarily controlled the situation behind the bench, but the problem escalated when fans behind one of the goals also began throwing rocks and explosives onto the field.
Local media said even oranges were thrown at players, and television images showed one bomb being thrown from the stands and exploding just a few meters (feet) from a group of police officers on the pitch. A few fans tried to break the fences separating them from the field.
Police used pepper spray and batons against the fans in the stands, but it was not enough. Referee Grazianni Maciel Rocha talked to authorities and decided to end the game, giving Avai the 2-0 win.
A victory at home was crucial to keep alive Paysandu's hopes of staying in the second division next year. The club is in relegation danger with eight rounds left.
Fan violence has become a common occurrence in Brazil in recent weeks.
World Cup organizers last week said more than 80 seats were destroyed at Arena Castelao by Fortaleza fans upset with the team missing out on promotion to the second division. A day earlier, more than 30 seats were damaged by fans of second-division club Ceara following a draw at the same venue.
That same weekend, police hit fans with batons inside Morumbi Stadium and later detained at least 30 people following a confrontation with supporters on one of the city's major avenues. Television images showed bloodied fans throwing punches at officers and some fans with small children trying to flee the chaos.
In Belo Horizonte, police had to use tear gas to contain Cruzeiro fans in the team's 1-0 loss to rival Atletico Mineiro. Police found homemade bombs with some of the fans, and television images showed at least one of the devices was hurled into the section where Atletico Mineiro fans were sitting.
Two weeks ago, a first-division match between Atletico Paranaense and Botafogo in the World Cup host city Curitiba was delayed at halftime because of fan fighting in the stands. The day before, a second-division game in the host city of Natal was delayed for nearly an hour as fans jumped onto the field to escape overcrowded stands.
No serious injuries were reported in the incidents.
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