Students and staff were evacuated from a high school in the U.S. state of Texas Wednesday after a bomb threat on the campus, local media reported. Tomball High School, some 55 km northwest of downtown Houston, was evacuated late Wednesday morning before lunchtime after school officials learned of a bomb threat, local media KHOU reported. Hundreds of students and staff were relocated to the school's track and field court while parents were notified through text messages. Police with sniffing dogs searched the campus and found no explosives. The school returned to normalcy two hours later, the report said. No information was available about the nature of the threat or how it was discovered. School officials told the media police will continue to investigate. Separately, a high school in San Antonio, Texas was locked down twice on Monday and Tuesday due to weapons threat. The school scrambled to lock down the campus on Monday after a student was found with loaded guns, including an AK-47 rifle. On the next day, a student received text message from an unknown number alleging someone carried a weapon on campus. The school was alarmed to place an immediate lockdown then. But police didn't find any weapon in a sweep of the campus.