TAMPA, FLORIDA — Two siblings were charged in connection with an improvised explosive device found outside MacDill Air Force Base in Tampa, Florida. The device was discovered at the base's visitor center on March 16.

The charged siblings are Alen Zheng and Ann Mary Zheng. Alen Zheng fled to China and remains there, according to a social media post by FBI Director Kash Patel. Ann Mary Zheng is in custody on charges of accessory and evidence tampering, according to the same social media post. She had her initial appearance before a judge on the same day the charges were announced.

The device was planted outside MacDill Air Force Base's visitor center on March 10, according to U.S. Attorney Gregory Kehoe. A 911 call reporting a bomb on MacDill Air Force Base was placed minutes after the device was left, according to Kehoe. The 911 caller did not provide a specific location for the bomb, according to Kehoe. MacDill personnel searched the base following the call but did not find the device immediately, according to Kehoe.

Law enforcement in Tampa responded to a report of a suspicious package at the visitor center near an entrance gate of MacDill Air Force Base on March 16. The device was ultimately discovered in a secluded area at the visitor center, according to Kehoe. Field screening of the suspicious package by investigators with the FBI's Tampa field office identified possible energetic materials.

U.S. Attorney Gregory Kehoe said the device did not detonate and could have been potentially very deadly. Indictments charged Alen Zheng with three counts: attempted damage of government property by explosion, unlawfully making a destructive device and possessing an unregistered destructive device. Ann Mary Zheng faces one count of evidence tampering and one count of accessory after the fact for helping her brother flee and tamper with evidence.

On March 11, Alen Zheng and Ann Mary Zheng purchased plane tickets to China and sold the vehicle that had been used to transport the device to the visitor center, according to Kehoe. Alen Zheng and Ann Mary Zheng left for China from Tampa on March 12, according to Kehoe. Ann Mary Zheng returned to the United States on March 17, according to Kehoe. Alen Zheng has not returned to the United States since fleeing, according to Kehoe.

"This FBI, working with our partners, will continue pursuing all those responsible and ensure they are brought to justice, no matter where they are," said FBI Director Kash Patel in a social media post. Investigators tied Alen Zheng to the phone used to place the 911 call about the bomb at MacDill Air Force Base on March 10, according to prosecutors. Law enforcement obtained a search warrant for Alen Zheng's home and found components consistent with the device, according to Kehoe.