The deadly shootings that left two people dead and 19 others injured at a house party in the suburbs of Houston, a port city in the U.S. state of Texas, Saturday was likely involved in gangs and there might be more shooters than originally thought, local authorities said Tuesday. Two suspects, who were detained Monday, made their first court appearance Tuesday morning, where both refused to plead guilty. Prosecutors said they believed the fatal party involved rival gangs. Police didn't found guns at the scene. "There's a lot more to it. It was a melee and people were running for their lives," the Houston Chronicle, the largest daily newspaper in Texas, quoted Katherine McDaniel, assistant Harris County District Attorney, as saying outside the courtroom. Witnesses said Tuesday that there were people at the party affiliated with gangs but no one would say for sure if the two suspects, identified as 18-year-old Randy Stewart and 21-year-old Willie Young, were affiliated with a gang. The two had previous arrest records. Saturday's tragedy happened at a home in the Houston suburb of Cypress late night when more than 100 people, mostly young adults and teens, were celebrating a birthday for a classmate turning 18. The house party turned violent when a first celebrating gunfire to the air led to random shootings into the crowd, prompting the panicked crowd into scrambling for life. Some even broke second- floor windows and jumped. A man and a woman were proclaimed killed, while 19 others were injured during the shootings. The dead were said to be high school students. Sixteen of the injured suffered gunshot wounds, some minor, while others suffered injuries from falls or stampede of people trying to escape, according to the local authorities. Social media was blamed for causing the tragedy. The birthday party was reportedly advertised on social media such as Facebook, Twitter, with the hope of attracting more strangers to the house party. The two suspects were held in the Harris County Jail with a bail of 250,000 U.S. dollars each. Neither has been charged in the deaths of the two victims so far.