The authorities in the eastern German state of Saxony struggled to explain on Thursday how a Syrian refugee suspected of planning an imminent terrorist attack had been able to kill himself in his jail cell, saying “we did everything possible to prevent it.”
The suspect, Jaber al-Bakr, 22, apparently hanged himself with his T-shirt. His death is almost certain to add to pressure on the state and federal authorities to improve coordination among the patchwork of agencies responsible for law enforcement.
Mr. Bakr, who was taken into custody by the police early Monday after he was turned in by other Syrian refugees, slipped through an initial attempt by the security services to capture him on Friday. He committed suicide Wednesday night in his Leipzig jail cell, a spokesman for the Justice Ministry in Saxony said.
“This should not have happened,” said Sebastian Gemkow, the justice minister for Saxony. “But it unfortunately did.”
The authorities suspected that Mr. Bakr had been in contact with the Islamic State and that he had been plotting to attack a major transportation hub in northern Germany. His death removed one possible avenue for investigators to learn more about how the extremist group is operating in the country, which has so far managed to avert a large-scale attack with mass casualties, as carried out by Islamist terrorists in neighboring France and Belgium.
Rolf Jacob, the director of the Leipzig jail where Mr. Bakr was admitted on Monday afternoon, said that prison officials had held several discussions with the suspect and his lawyer. According to a senior intelligence official, who insisted on anonymity to discuss a sensitive national security case, Mr. Bakr had been refusing to cooperate with investigators.
The special police who failed to arrest Mr. Bakr last week had already come in for criticism after he was able to elude capture despite heavy surveillance and a raid on his apartment in Chemnitz, about 50 miles south of Leipzig.
A prison psychologist had assessed Mr. Bakr and concluded that he had been calm and that there had been no particular danger of suicide, Mr. Jacob said at a news conference that was broadcast live in Germany.
Initially, prison authorities had decided that they should check on the prisoner every 15 minutes, he said. That interval was broadened on Wednesday to every 30 minutes, he added. Confining a prisoner to a cell with constant monitoring requires a special procedure that officials did not detail.
Nonetheless, Mr. Jacob said, a guard decided 15 minutes after a regular check at 7:30 p.m. to check again. She saw that Mr. Bakr had hanged himself, apparently using his shirt on bars that separated his cell from the door.
Medical help and other guards were immediately summoned, and they attempted to revive Mr. Bakr before he was declared dead at 8:15 p.m.
The police had found more than three pounds of the explosive TATP, or triacetone triperoxide — the explosive used in terrorist attacks in Paris and Brussels — in his apartment, and officials say they believe that he had been in a very advanced stage of a plot to carry out an attack.
Mr. Bakr sought refuge over the weekend with other Syrians in Leipzig, although his relationship to those fellow refugees was not immediately clear.
One of the Syrians, who would give his name only as Mohammed A. because of the fear that his family in Syria could be targeted if he was identified, told the German news channel N-TV that the suspect had called him out of the blue on Saturday asking for a place to stay.
The next day, Mohammed A. said, when the police released a version of the search warrant translated into Arabic, he realized who he was sheltering in his home. He added that he had called a couple of friends and had asked them to go to his home and tie up Mr. Bakr to prevent him from leaving.
He tried calling the police, he said, but, unable to speak enough German, he instead returned home, took a picture of the suspect with his cellphone and then went to the nearest police station. After waiting for an hour, he said he had been able to show officers the photograph of the suspect, his feet bound with electrical extension cords. Officers then took immediate action.
Nearly a million asylum seekers, a majority from Syria, entered Germany without prior background screening in 2015, raising fears that some members of the Islamic State had been able to sneak in by hiding among the refugees who had made their way to the country.