Jaber al-Bakr, 22, had been "quiet and calm, there was no indication of emotional issues," said Rolf Jacob, who heads the prison in the eastern city of Leipzig.
Although the detainee had begun a hunger strike following his imprisonment on Monday, a "very experienced psychologist" who interviewed him had assessed that "there was no acute suicide risk", Jacob said.
The psychologist therefore suggested that the regular checks, which were initially set at 15 minute intervals, be reduced to half hourly from Tuesday, said Jacob.
Bakr's death in custody marks a second official fiasco after police commandos earlier botched his arrest, sparking a nationwide weekend-long manhunt.
The suspect was eventually captured by three fellow Syrians who tied him up and handed him to police.
Interior Minister Thomas de Maiziere said the suicide had "obviously hampered investigations" into the alleged terror plot and posed a "setback in the search for other accomplices, backers, networks and such.
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