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THE HAGUE, Netherlands (AP) — Dutch police and prosecutors on Wednesday were pursuing "every lead there is" and questioning two suspects to establish whether the deadly shooting on a tram in the central city of Utrecht was an act of terror.

Officers from a specialized arrest team detained a 40-year-old man in Utrecht on Tuesday and released two other men detained earlier, said police spokesman Joost Lanshage.

The alleged shooter, 37-year-old Gokmen Tanis, remains in custody.

Prosecutors have until Friday to question the Turkey-born suspect before he must appear before an investigating judge who could extend his detention.

Monday morning's attack saw a gunman opening fire on a tram in a residential neighborhood, killing two men and a woman and seriously injuring three others.

Fearing more than one shooter was active, authorities locked down the city for hours — halting public transport and advising residents to stay indoors — until Tanis was arrested.

Prosecution spokesman Ties Kortmann said that the investigation was continuing into the motive of the suspects and into the possible involvement of the man arrested Tuesday.

"We are looking at the role of the new suspect," he added. The suspect's identity was not released.

Prosecutors have said they are seriously considering an extremist motive after finding a note in a suspected getaway car after the attack, and because of the nature of the shooting. They have not ruled out other possible motives.

"We are looking into every lead there is," Lanshage said.

Prosecutors said Tuesday that investigations had not yet determined any relationship between the alleged shooter and the victims.

Meanwhile, a crowdfunding initiative to pay for the funeral of one of the victims had already attracted nearly 60,000 euros ($68,000) by early Wednesday morning.

On a crowd-funding website, a neighbor of the 19-year-old woman killed in the attack appealed for donations saying the victim's father "is not well off."

"To prevent him having more financial concerns because of the unfair death of his daughter, I want to support him financially by collecting money," wrote the neighbor, who was identified on the funding site as Martje Beniest-Kleppe.

37-year-old Gokmen Tanis is led away by police in Utrecht, Netherlands, Monday March 18, 2019, after a shooting incident on a tram. A gunman killed three people and wounded five during a mid-morning tram ride Monday in the Dutch city of Utrecht. Authorities seized a Turkish-born suspect after a manhunt that convulsed the historic city of nearly 350,000 people for most of the day. (Foto de Volkskrant via AP)  NETHERLANDS OUT NOT FOR USE IN THE NETHERLANDS
People lay flowers at a makeshift memorial site for the victims of a shooting incident in a tram in Utrecht, Netherlands, Tuesday, March 19, 2019. A gunman killed three people and wounded others on a tram in the central Dutch city of Utrecht Monday March 18, 2019. (AP Photo/Peter Dejong)
Women representing Utrecht's Muslim community lay a wreath at a makeshift memorial for the victims of a shooting incident in a tram in Utrecht, Netherlands, Tuesday, March 19, 2019. A gunman killed three people and wounded others on a tram in the central Dutch city of Utrecht Monday March 18, 2019. (AP Photo/Peter Dejong)
Children lay flowers at a makeshift memorial site for the victims of a shooting incident in a tram in Utrecht, Netherlands, Tuesday, March 19, 2019. A gunman killed three people and wounded others on a tram in the central Dutch city of Utrecht Monday March 18, 2019. (AP Photo/Peter Dejong)
Dutch Prime Minister Mark Rutte expresses his gratitude to Dutch police officers after laying flowers at a makeshift memorial for victims of a shooting incident in a tram in Utrecht, Netherlands, Tuesday, March 19, 2019. A gunman killed three people and wounded others on a tram in the central Dutch city of Utrecht Monday March 18, 2019. (AP Photo/Peter Dejong)
Dutch Prime Minister Mark Rutte expresses his gratitude to Dutch police officers after laying flowers at a makeshift memorial for victims of a shooting incident in a tram in Utrecht, Netherlands, Tuesday, March 19, 2019. A gunman killed three people and wounded others on a tram in the central Dutch city of Utrecht Monday March 18, 2019. (AP Photo/Peter Dejong)
Dutch Prime Minister Mark Rutte, right, and Justice Minister Ferd Grapperhaus arrive at a makeshift memorial for victims of a shooting incident in a tram in Utrecht, Netherlands, Tuesday, March 19, 2019. A gunman killed three people and wounded others on a tram in the central Dutch city of Utrecht Monday March 18, 2019. (AP Photo/Peter Dejong)
Mourners pay heir respect at a makeshift memorial at the site of a shooting incident in a tram in Utrecht, Netherlands, Tuesday, March 19, 2019. A gunman killed three people and wounded others on a tram in the central Dutch city of Utrecht Monday March 18, 2019. (AP Photo/Peter Dejong)
The picture of one of the three victims sits amidst flowers as mourners pay their respect at the site of a shooting incident in a tram in Utrecht, Netherlands, Tuesday, March 19, 2019. A gunman killed three people and wounded others on a tram in the central Dutch city of Utrecht Monday March 18, 2019. (AP Photo/Peter Dejong)