Last Updated Nov 23, 2015 6:27 AM EST
BRUSSELS -- Belgium's capital would normally be bustling on a Monday morning, but this Monday morning is different. CBS News correspondent Debora Patta reported most of the shops were still shuttered and the metro was shut down as the country woke up to a third day of security lockdown.
Belgian authorities have repeatedly warned that a Paris-like attack is imminent -- likely targeting shopping areas and public transport.
Drastic measures were put into place, including closing down schools for the first time in the country's history since World War II.
The heightened alert even spread as far as Washington D.C., where Department of Homeland Security chief Jeh Johnson ordered additional checks for passengers boarding flights in Belgium destined for the U.S.
DHS "continually assesses the global threat environment and re-evaluates the measures taken to promote aviation security. As part of this ongoing process, DHS Secretary Jeh Johnson has directed the Transportation Security Administration (TSA) to implement enhanced security measures for departures to the U.S. from Brussels National Airport," a statement released Monday said.
The statement said passengers may be asked to power up electronic devices and any that would not power up could be removed. It warned travellers to give extra time for check in at Brussels.
The urgent sound of police sirens was the only noise that punctuated an unusually quiet city center Sunday night. Security forces were bolstered across the capital; soldiers in full camouflage on patrol with police officers. Police cordons blocked the usually choked thoroughfares.
Residents were urged to follow police instructions -- and to stay away from windows in some areas.
Then, in a series of coordinated strikes, police carried out 19 raids late into the night, right across the capital city.
At a hastily-convened midnight news conference, Belgian Federal Prosecutor Eric Van Der Spyt announced that 16 people had been arrested in the operations. That figure went up Monday morning, when the prosecutor's office said an additional five homes around Brussels and two in the city of Liege had been raided, netting five more suspects.
"Until now, no firearms or explosives were found. Salah Abdeslam is not -- not -- among the persons arrested during the searches," said Van Der Spyt, referring to Europe's most-wanted man. And so a suspect in the Paris attacks who evaded police on that bloody Friday night and managed to slip back into Belgium, remains on the run.
There had been reports that Abdeslam was spotted Sunday night in Liege, a city about 60 miles from Brussels, near the German and Dutch borders. The prosecutor said Monday, however, that while a car did try and speed away from a roadside check, there was not believed to be any link to the suspect.
Van Der Spyt said only that "specific elements of the enquiry" into the attacks on the neighboring nation "necessitated the operation of Sunday night." Most of the suspects in the Paris carnage lived or had links to the Belgian capital, and specifically to the Molenbeek neighborhood where Sunday night's raids were focused.
Abdeslam's brother Mohammed appealed on local television, urging Salah to hand himself over to police.
"I think that effectively at the last minute Salah decided to change course," he said. "He perhaps saw or heard something, and decided not to carry out his plans."
But Belgian police have their hands full; they're searching not only for Abdeslam, but for a number of other people they believe are linked to the terror plot.
The failure to capture Abdeslam thus far will bring no comfort to Belgians, who are beginning to wonder how long the stringent security measures freezing life in their capital can be kept up.