The match started in party atmosphere at a packed Monumental with the traditional ticker tape welcome when the players took to the field, but degenerated into sporadic incidents of violence after the final whistle.
"There were 25 people hurt but no-one has died," Alberto Crescenti of the state emergency medical service told sports daily Ole after rumours circulated that two security guards had been killed in an attack by Boca fans.
"There is no-one in critical condition... although some people have been taken to hospital," added a spokesman for the private firm that provided security personnel at the giant 1978 World Cup stadium.
Midfielder Erviti's scrambled goal came from a quick break after the Boca defence had blocked a shot at the other end from River captain David Trezeguet, who was attempting to mark his first big Buenos Aires derby with a goal.
"The goal is important because of the difficult times Boca is having," Erviti told reporters, referring to his team's poor form with only three points from their last five matches.
Midfielder Leonardo Ponzio repeated his trick of River's previous home match when he hit a right-footed free-kick from 30 metres out on the left inside the near post with goalkeeper Agustin Orion reacting too late.
Nippy Uruguayan striker Rodrigo Mora, a thorn in the side of Boca's defence throughout the match, put River two up in the 70th minute with a superb shot from a tight angle on the right.
Five minutes later, though, substitute defender Leandro Gonzalez Pires gave away a penalty converted by Boca's Uruguayan striker Santiago Silva.
Newell's Old Boys top the table with 26 points after Saturday's 2-1 home win over title-holders Arsenal in Rosario, where striker Ignacio Scocco scored twice including a brilliant overhead goal.
Newell's were a man short for 30 minutes after former Argentina defender Gabriel Heinze was sent off for a second booking.
