(CNN)Three Chinese nationals were sentenced to prison Thursday for entering a restricted area at a naval base in Key West, Florida, to take photos.
Chinese national Liao Lyuyou, 27, was sentenced to 12 months in prison after pleading guilty to illegally entering the restricted area within Naval Air Station Key West in December and taking photographs and video, according to the US Attorney's office of the Southern District of Florida.
In a separate case, Jielun Zhang, 25, and Yuhao Wang, 24, were sentenced to 12 months and nine months in prison, respectively. Both men pleaded guilty to illegally entering a restricted area within the same naval base as Liao. They were also taking pictures, according to the US Attorney's office of the Southern District of Florida.
Liao was arrested on December 26 for entering the restricted area and taking photos of an annex and other government buildings near sensitive military facilities. He was verbally warned not to but did it anyway, according to court documents.
Liao had circumvented a security fence with "numerous warnings posted" on it, the documents said, and continued to walk in the restricted area and take photos after "witnesses verbally warned him." He later told officials that he reads and understands English better than he can speak it.
According to the documents, Liao stated he was trying to take photos of the sunrise after US military police approached him. He gave them permission to look at his camera where they saw images of the Truman Annex at the facility as well as photos of other government buildings in the area.
A week later, Jielun and Yuhao approached the guard station in a blue Hyundai on January 4 at the Sigsbee Annex at the Naval Air Station in Key West, according to the criminal complaint.
When Jielun and Yuhao could not provide a military identification, a navy security officer told them to make a U-turn and exit the facility.
Jielun and Yuhaog did not follow instructions and instead stayed at the facility for approximately 30 minutes, according to the complaint.
Navy security officers obtained consent to look at the cell phones and the camera in their possession and observed photos of the Sigsbee Annex property, including US military structures on Fleming Key.
The incidents happened shortly after two Chinese Embassy officials were "secretly expelled" by the US last year after they entered a "sensitive" military base near Norfolk, Virginia, according to The New York Times.
The Times said half a dozen people with knowledge of the expulsions said US officials believe "at least one of the Chinese officials, who were with their wives, was an intelligence officer operating under diplomatic cover."