Motorcyles sit in the parking lot of the Twin Peaks restaurant, the scene of a motorcyle gang shootout, May 18, 2015 in Waco, Texas
Washington (AFP) - A deadly biker brawl in Waco, Texas apparently was set off when a motorcycle gang showed up uninvited at a gathering of rival biker groups, police said.
Authorities said they are still piecing together the events that led up to Sunday's bloodbath at the Twin Peaks Sports Bar and Grill that involved some 170 motorcycle gang members and left nine people dead.
Some of the dead might have been shot by police officers, said Waco police spokesman Patrick Swanton, who said it is impossible to determine how many of those were killed by police gunfire "until autopsies are complete and we get those final results."
Complicating the investigation, Swanton said, is that many of the bikers questioned have been less than fully cooperative.
"It is a lengthy process for those investigators to attempt to determine exactly what occurred when you have people not being truthful with us about what went on inside and outside the restaurant," he said.
The police spokesman said initial investigations suggested Sunday's brawl was the result of "a turf war."
"There was a planned meeting of one group of biker members. That meeting is a coalition of several bike groups that were invited to come to Twin Peaks restaurant," he said.
"We know an additional biker gang that was not invited to this meeting showed up," he said, adding that other leads suggest the fight began as an altercation between gang members in the restaurant restroom.
- Huge crime scene -
Contributing factors may have been an altercation over a parking space, he said, adding they were also looking into reports that "somebody had their foot run over and started the disturbance in the parking lot."
The violence led to the arrests of 170 people who were charged with organized crime resulting in death -- an offense that can be punished by death in Texas.
Bond has been set at $1 million for the bikers involved. Three of the defendants, however, were initially released on much lower bonds.
In a late afternoon press conference, Swanton emphasized that the men "were not mistakenly released" and that they had a right to the bonds which were set "very early."
Nonetheless a judge had revoked the lower bonds, replaced them with $1 million bonds and reissued the bikers' arrest warrants, he said.
The brawl, which eventually spilled into an outdoor patio area and the parking lot, creating a huge, unwieldy crime scene.
"We have picked up most of the important pieces of evidence, blood evidence, bullet fragments, shell casings, and weapons," said Swanton, who added that authorities have scores of cars and motorbikes still at the scene which will have to be removed and combed for evidence.
"There are approximately 135 motorcycles that will need to be removed from the crime scene and transported to a secure location," he said.
In addition to the dead, police said 18 people were injured, seven of whom were still in the hospital on Tuesday.
The Twin Peaks is located in a popular Waco shopping and dining center known as the Central Texas Marketplace.
Among those arrested were bikers wearing the insignias of the Cossacks, the Scimitars and the Bandidos groups.
In the United States they are particularly associated with gun-running and drug-trafficking, and some biker clubs or their chapters have been formally designated as organized crime groups by the Federal Bureau of Investigation (FBI).
Waco is in central Texas and has a population of about 129,000.