NISD officials said they managed to inspect all 53 school buses in 75 minutes. Many of those checks included stopping buses, evacuating passengers and later reloading students to continue along their routes. Some buses were stopped at various schools where they had substantial delays before being given the "all clear." NISD Chief of Police Doug Ploch said the Nacogdoches Police Department received an anonymous call at approximately 3 p.m. Monday, just as school was releasing on most campuses. The caller did not specify which bus had been targeted, and Ploch said that by the time call was made, almost all NISD buses had left the bus barn for their respective campuses. And because of the non-specific nature of the threat, an officer at Raguet Elementary stopped not only Southwest Student Transportation buses, but all buses, including those operated by private after-school facilities. "The NISD Police Department coordinated with the NPD to begin searching all buses, whether they were in the bus barn or already on individual campuses," Ploch said. "The city officers went to the elementary campuses and began checking buses, along with the bus drivers, and we went to the high school and junior high campuses. The NPD officers did a great job of responding quickly and professionally." Ploch said once the threat was received and the bus barn notified, NISD's transportation provider, Southwest Student Transportation, began contacting their drivers via radios on the buses. However, at least two NISD bus drivers and three private after-school providers had no idea why a Nacogdoches police officer told them they had to park their bus and unload all of the children at Raguet Elementary. Two of the bus drivers who were stopped said no one had told them anything. The officer who flagged them down simply said they had to evacuate the bus and wait inside until further orders. As students disembarked the bus, the questions started. "Why are we stopping here? I've never even been to this school." "Is this an elementary school?" "How long are we going to have to stay?" The bus drivers were short on answers. One SST driver, stopped at Raguet, said no one had told her what was going on, but she assumed "it was something like that." Another bus driver, who apparently got the message, pulled over near Raguet Elementary to make a quick sweep of the bus. He exited the bus to check his cell phone, boarded the bus loaded with students and continued past the school while others were being stopped. An SST spokesman said all buses have radios and that a radio message was sent to the buses, but that there are "dead" areas within the city and county, and some drivers may have missed the message. Ploch said SST has an internal procedure to deal with emergency situations, such as a bomb threat, and each bus driver checked his or her own bus before allowing children to board. At five minutes after 4 p.m., five buses at Raguet Elementary had not been checked for explosive devices and all of the students remained inside the school. But Ploch said that by 4:15, all children throughout the district were on their buses and heading home. "Obviously, there was no bomb located on any NISD bus," Ploch said. The investigation into who made the bomb threat will continue. Sentinel staff writer Johnny Johnson contributed to this report.