Qatar says investigators are examining possible design flaws that funneled dense smoke into areas around a daycare center in the country's biggest mall, where 13 children and four workers died in a fire.
Qatar's Interior Ministry says experts will study whether corridors and stairways in the Villaggio mall trapped heat and smoke in Monday's blaze, which also killed two firefighters.
Officials also are studying malfunctions in the sprinkler system and possible shortcomings in other safety measures, including alarms.
Among those in detention Thursday is the daycare center's owner, Imran al-Kuwari, daughter of Qatar's culture minister. It is not clear whether charges will be filed.
The findings from the investigation are expected next week.