Plot Foiled? 5 Moroccan Muslims Caught Sneaking Inside TX Courthouse at 2 A.M.

What were three French-Moroccan Muslims in their twenties doing with photos of infrastructure and high tech camera equipment inside the Bexar County Courthouse in San Antonio at almost 2 o'clock this morning?

Nobody has given any good answers yet, and concerns about a possible terrorism plot remain high.

(Related: Emergency landing after man shouts "You're all going to die" and "Allahu Akbar" on Southwest Flight)

Officers of the FBI's Joint Terrorism Task Force and the Department of Homeland security have the three suspicious individuals in custody and are trying to find out if a terrorism-related plot was disrupted. The men apparently entered the building by sneaking through a window.

The men appeared to have entered the country on legal visas from Heathrow airport and had traveled extensively throughout the U.S. According to WOIA radio, officials say the men had "photographs of infrastructure" including photos of shopping malls, water systems, courthouses and other public buildings which they say were taken in cities nationwide."

In response to the possible threat early this morning, police cordoned off two square blocks of downtown San Antonio and bomb-sniffing dogs were deployed throughout the courthouse. After a couple of hours, police reopened the streets as no danger was detected.

Investigators are keeping the case close-hold, but one law enforcement officer reportedly said of the three Muslim men that "the fact why they can't explain why they are in the building at 1:22 in the morning raises questions."

It remained unclear if a military intelligence convention a few blocks away that was set to have high level speakers, including White House personnel, was in any way related.

UPDATE:

KSAT-TV reports that five men have been detained in relation to the break-in and that they are not cooperating with police. Two of the men are apparently on the FBI's watch list and they came into the country on 9/11:

The men, who are in their 20s, were detained after sheriff's officials determined they broke into the building through a door on the fourth floor, sheriff's officials said. Three men were located inside the building and two were found outside near a recreational vehicle.

Surveillance video showed the men walking into the building with an item in their hands, but they did not have the item when they walked out of the courthouse, sheriff's officials said. Investigators have not said whether that item was recovered or what it may be.

The RV contained several documents and proof the men had been traveling across the country for some time, sheriff's officials said.

Sources told ABC News that three of the men appear to be of Morroccan descent and that the men had pictures of courthouses and water systems from around the country.

UPDATE II:

The local judge says the scare may have just been a drunken "prank." Read our follow-up story about the latest developments here.