An alleged collaborator of the main suspect in the Istanbul New Year’s nightclub attack was released in Denmark on Tuesday, according to Danish police.

Southeast Jutland Police Headquarters said in a statement that Ibrahimjon Asparov, 42, was released after being held since July.

The statement said the Uzbek-origin suspect had been held due to an extradition request by Turkey, but the request was turned down, and he faced no charges in Denmark.

The investigation of Asparov is ongoing, the statement said.

At Turkey’s request, Asparov was detained on June 29 in southeastern Jutland with the help of Danish intelligence, was later released, but was again taken into custody on July 20.

Asparov is accused of supplying weapons and ammunition to Abdulgadir Masharipov, the main suspect in the Reina nightclub attack.

At least 39 people, including a police officer, were killed when a gunman opened fire on partygoers at the nightclub in Istanbul’s Ortakoy district in the early hours of Jan. 1 this year.

On Jan. 16, Masharipov was captured by police in Istanbul’s Esenyurt district.

Four other suspects, including a male of Kyrgyz origin and three women, were also detained.