FORT LAUDERDALE, Fla. (AP) — The FBI announced that a suspicious package found outside a gate at MacDill Air Force Base in Tampa earlier this week contained 'possible energetic materials.' An analysis of the material has not yet been completed as the investigation continues, according to a statement from the FBI Tampa.

Energetic materials generally include explosive materials, fuels, or propellants, but specifics regarding the materials in the package have not been clarified with the FBI.

On the same day, the base implemented a shelter-in-place order due to a received threat. 'We take all threats seriously and are taking appropriate measures to prioritize the safety and security of our installation,' MacDill officials stated, while confirming that they would not disclose specific security measures.

After approximately two hours, the shelter-in-place order was lifted, but officials indicated that heightened security remains in place.

Overnight on Tuesday, the base began operating under Force Protection Charlie, the second-highest military security designation, which enables officials to proactively implement deliberate security measures.

All personnel on base have been advised to remain vigilant, adhere to security forces' instructions, and promptly report any suspicious activities.

MacDill is home to the U.S. Central Command (CENTCOM), which oversees military operations in the Middle East and beyond, and it has maintained a state of heightened alert since the onset of tensions in Iran. Recently, the base mourned the loss of six crew members from a KC-135 refueling aircraft in a tragic incident while supporting operations against Iran.