After a dry ice bomb explosion in a Los Angeles International Airport terminal on Sunday, October 13, three similar bombs turned up in a different terminal the next day, prompting a major search effort involving airport police, the Los Angeles police bomb squad, and the FBI.

At around 7 p.m. on October 13, an airport worker heard an explosion in an empty men's bathroom in a restricted area within Terminal 2. A 20-oz plastic bottle containing dry ice was found in the restroom.

Terminal 2 was closed and evacuated, and flights were held until 8:45 p.m. that evening while the Los Angeles police bomb squad searched the area. No damage or injuries were reported.

At 8:30 p.m. the following night, another explosion took place in the Tom Bradley International Terminal, also in an area restricted to employees. This explosion was caused by a similar dry ice bomb. Investigations uncovered two more of such devices within the terminal. No flights were disrupted.

Airport spokeswoman Katherine Alvarado said the bottles were "harmless."

Law enforcement sources believe that the incidents are likely to be pranks with no known connection to terrorism, according to NBC. But Los Angeles Police Sergeant Karla Ortiz said it was too early to discuss suspects or motives.

"We have to finish our investigations to find out what the cause was," Ortiz told NBC. "We always do our best to prevent such incidents but we will be keeping our eyes peeled following these similar events."