Neighbors help clean up the house where a shooting incident happened duting a family party in Houston surburb of Cypress, US, Nov 10, 2013. [Photo/Xinhua]

HOUSTON - Two high school students were killed and 19 others, most of them teens, wounded when a celebratory gunfire led to random shootings at a massive house party in a suburb of the US city of Houston, authorities said Sunday.

The incident happened around 11:00 pm Saturday (0500 GMT Sunday) when nearly 100 people, mostly young adults and teens, were celebrating a birthday at a home in Houston suburb of Cypress, the Harris County Sheriff's Office told reporters.

Sheriff Adrian Garcia described the event as a "birthday party gone wild", saying evidence indicated that there was no one-on-one confrontation prior to the shooting.

The initial investigation showed that someone pulled a pistol and fired one celebratory shot into the air, he said.

"Someone else recklessly reacted to the gunfire and shot into the crowd," Garcia said, adding that about 10 shots were fired.

The incident was "a horrible combination of immaturity, access to a firearm and the inability to control oneself", said the sheriff.

Two Cypress Springs High School students, an 18-year-old male and a 16-year-old female, were killed, while 19 others were injured during the shooting, Garcia said. One of the victims died at the scene, while the other died at a hospital.

Eighteen of those who were injured suffered gunshot wounds and another victim suffered a broken leg while trying to escape, he said. Media reports earlier put the toll at two killed and 22 injured.

Garcia blamed social media for causing the tragedy, saying promoting the party on social media likely invited strangers to the home. The birthday party was reportedly advertised on Twitter and Instagram.

"Anytime you promote a birthday party on social media, you have no control over who to expect at your door," he said. "What it does is indicate, that your saying to the social media world, 'I don't know who you are, but you're invited.' That's not a good practice."

No firearms were recovered at the scene, but several bullet casings were found, the sheriff said. No drugs or alcohol are suspected in the shooting.

Pools of blood were visible outside the two-story brick home Sunday morning, and the garage door was bent after people pushed it upward while trying to escape.

Witnesses spoke of a chaotic scene where the panicked crowd scrambled to run for their lives. Some of them broke second-floor windows and jumped. When deputies arrived, they saw some people lying on the ground and others running.

Teenager Shaniqua Brown who attended the party told the Houston Chronicle, the largest daily newspaper in Texas, that Saturday evening's birthday party "was not rowdy at all", and many people were dancing when they heard the shots.

Gunshots began in the house and continued outside as people ran to the streets seeking cover, said the 17-year-old girl. She said she saw one gunman when she ran outside.

Another witness who identified himself as 19-year-old A. Henry told the Chronicle that he was toward the kitchen when the gunfire erupted. He said he heard between 10 and 12 shots fired and that the shooting seemed to last between three to five minutes.

Another witness named Karen Briones said she drove to the scene after hearing the gunshots. She was visiting relatives who live in the other side of the neighborhood. "Girls were crying and screaming, banging on people's doors asking them for help and to call 911," Briones told the Chronicle.

Authorities are now searching for two suspects, both male at the age of 17 and 22, in connection with the shooting.