The Belgian capital began cautiously easing its lockdown Wednesday, opening schools and some metro stations after unprecedented security measures imposed in response to the threat of a Paris-style attack.

Soldiers and police still guarded sites including malls, hotels and public transportation in a reminder that Brussels remains on edge. About half the city's metro stations reopened, while 300 additional officers were assigned to protect schools.

Besides the widespread security clampdown, investigators also sought fresh leads in the manhunt for a key suspect in the Nov. 13 Paris bloodshed after acknowledging that he slipped through unrecognized by Belgian authorities just hours after the attacks.

The search for Salah Abdeslam - believed to have a role in the Paris attacks - and fears of a similar rampage on home soil led Belgian authorities to impose the sweeping security measures. The steps were particularly tight in Brussels, home to the headquarters of NATO and many European Union offices.

In recent days, security forces have arrested dozens of people in Belgium and neighboring France. Belgian Prime Minister Charles Michel said that extra security measures will remain in place at least until Monday, with the threat of an attack still "serious and imminent."

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Despite the reopening of the metro, many workers still appeared to have avoided going to their jobs in the capital as the terror alert remained at its highest possible level.

"It seems like lots of people are still afraid," said Katie Goeman, 39, a teacher, noting that the streets were not as busy as usual. "It's sad. I don't think people should let fear take over their lives."

Store owners are concerned about the economic impact on their businesses. Stefany Montoya, who works in a shop selling tourist items in the city center, said she opened her store on Tuesday but sold only $38 worth of goods.

"Tourists stayed away, they are not coming back any time soon," she said. "It's a disaster."

After the carnage in Paris, investigations quickly led to Belgium.

Abdelhamid Abaaoud, the alleged mastermind of the attacks, was from the Brussels neighborhood of Molenbeek and is believed to have spent time in Syria. Abdeslam, a 26-year-old French national, lived in Molenbeek with his brother, who was among the seven attackers who died in Paris.

The attackers killed at least 130 people in the deadliest rampage on French soil since World War II.

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French officials have accused Belgian intelligence and security services of missing opportunities in the case. On Tuesday, the Belgian federal prosecutor's office said Abdeslam was "checked" by police the morning after the Paris attacks while riding in a car with two other people on a highway to Brussels. They were allowed to go on their way.

But Belgian police subsequently arrested Mohammed Amri, the owner of the car, and Hamza Attou, one of the passengers, on Nov. 15 on terrorism charges, the office said.

Another person arrested on the same charges was a 39-year-old Moroccan from Molenbeek, identified only as Lazez A., the prosecutor's office said, noting that two pistols and traces of blood were found in his vehicle.

Belgium's prosecutor's office on Tuesday identified an additional suspect in connection with the attacks as Ali. O, a 31-year-old French national also living in Molenbeek, saying he drove a vehicle for Abdeslam after the Paris attacks.

Meanwhile, an international arrest warrant has been issued for another man, Mohamed Abrini, 30, who was spotted two days before the Paris attacks in a vehicle with Abdeslam on a highway heading toward the French capital, prosecutors said.

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