Four people were stabbed in Lawrence early Sunday when a fight broke out after a birthday party, police said. A gathering at 23 Oregon Ave. took a wrong turn when partygoers started fighting around 4 a.m., said Police Chief John Romero. “According to witnesses, one combatant was armed with a machete,” he said. Romero said it was not immediately clear what prompted the violence. The four victims were first taken to Lawrence General Hospital, but two had to be transported to a Boston hospital with more serious injuries, Romero said. Lawrence police and State Police assigned to Essex District Attorney Jonathan W. Blodgett’s office are investigating. No arrests have been made, police said.Melissa Werthmann can be reached at firstname.lastname@example.org.